21 ms·

Why aren’t we talking more about airborne transmission?

301 points by KoftaBob 6y ago

CogentHedgehog 6y ago
Short-distance aerosol transmission changes things a bit: * Social distancing isn't enough to guarantee safety in indoors spaces: bad news for bars, clubs, gyms, concerts, and restaurants * Outdoors spaces are probably safer than we previously thought * Indoor mask-wearing becomes CRITICAL in public spaces * Indoor ventilation becomes extra important, using fresh air from outside or filtered/UV-sanitized air * Indoor air purifiers with HEPA ratings or UV sterilizer features may become valuable But the same overall guidance still applies: avoid crowds, wear a mask, keep your distance, outdoors activities are safer than indoors activities
- DanBC 6y ago
  > Indoor mask-wearing becomes CRITICAL in public spaces Mask wearing provides minimal benefits against droplet transmission, but they do nothing at all for small droplet aerosol transmission.
  - misanthropian00 6y ago
    What do you consider a small droplet? The masks are tested with 0.3 micron droplets. Do you have a source?
  - keenmaster 6y ago
    Studies have found that a combination of multi-layered cotton and chiffon/silk masks prevents intake of both large and small droplets. Silk/chiffon act magnetically on smaller particles to keep you from breathing them in, while the thick cotton layers stop large droplets. The aggregate effect is similar to N95, but more washable and reusable. It blows my mind that this was discovered a couple months ago and the government still hasn’t funded the mass production of such masks. After I read the study, I bought 2 masks on Etsy.com: a multilayered cotton mask and a silk mask. I wear both when I go out. What’s great is that I don’t just protect others from me, but I also protect myself from others to a large extent (as opposed to just wearing the cotton mask). As for comfort, silk is light and thin, so it doesn’t add any noticeable discomfort on top of the cotton mask. https://news.uchicago.edu/story/homemade-masks-made-silk-and-cotton-may-boost-protection https://news.uchicago.edu/story/homemade-masks-made-silk-and... Note: Newer studies have found that even just a thick cotton mask does somewhat protect you (not as much as cotton + silk of course, but they protect others from you quite effectively). You still need to be careful, generally avoid indoor environments with strangers, and socially distance. Not that that disclaimer is super necessary, because other studies have found that masks do not make people behave more recklessly :) If anything, they make you more careful and acutely aware of COVID risks.
    - DanBC 6y ago
      > Newer studies have found that even just a thick cotton mask does somewhat protect you No they haven't. If the effect of masks was so strong it would be easy to find that when we do trials. We've done the trials and we struggle to see the effect. Once we drop down the quality requirements we start to see an effect, but even that is mild. https://www.thelancet.com/action/showPdf?pii=S0140-6736%2820%2931142-9 https://www.thelancet.com/action/showPdf?pii=S0140-6736%2820... > Although direct evidence is limited, the optimum use of face masks, in particular N95 or similar respirators in health-care settings and 12–16-layer cotton or surgical masks in the community, could depend on contextual factors; action is needed at all levels to address the paucity of better evidence. Eye protection might provide additional benefits. Globally collaborative and well conducted studies, including randomised trials, of different personal protective strategies are needed regardless of the challenges, but this systematic appraisal of currently best available evidence could be considered to inform interim guidance There's no way to spin phrases like "direct evidence is limited" and "paucity of evidence" to mean "we've got good quality evidence that shows an effect".
  - CogentHedgehog 6y ago
    That's actually the opposite of what the evidence shows. Masks - even crappy ones, with poor mask protocol - dramatically cut infections https://arstechnica.com/science/2020/06/modeling-the-impact-of-face-masks-on-the-covid-19-pandemic/ https://arstechnica.com/science/2020/06/modeling-the-impact-... Citation: https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818 https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818 Remember: even if a mask doesn't effectively filter out very small particles, it still restricts the velocity of air passing through it. This means aerosolized particles will not travel as far.
    - DanBC 6y ago
      About your arstechnica link: if masks don't work all that effectively you need huge numbers of people to wear them to prevent a single infection. https://www.fhi.no/globalassets/dokumenterfiler/rapporter/2020/should-individuals-in-the-community-without-respiratory-symptoms-wear-facemasks-to-reduce-the-spread-of-covid-19-report-2020.pdf https://www.fhi.no/globalassets/dokumenterfiler/rapporter/20... > Non-medical facemasks include a variety of products. There is no reliable evidence of the effectiveness of non-medical facemasks in community settings. There is likely to be substantial variation in effectiveness between products. However, there is only limited evidence from laboratory studies of potential differences in effectiveness when different products are used in the community. > Given the low prevalence of COVID-19 currently, even if facemasks are assumed to be effective, the difference in infection rates between using facemasks and not using facemasks would be small.Assuming that 20% of people infectious with SARS-CoV-2 do not have symptoms,and assuming a risk reduction of 40% for wearing facemask, 200000 people would need to wear facemasks to prevent one new infection per week in the current epide-miological situation. Here's all the science: we don't know if masks work or not. https://www.cebm.net/covid-19/masking-lack-of-evidence-with-politics/ https://www.cebm.net/covid-19/masking-lack-of-evidence-with-... They have a plausible mechanism of action, but they also have plausible mechanisms of harm. The above link includes one trial where they appeared to be harmful: > It is debatable whether any of these results could be applied to the transmission of SARs-CoV-2. Only one randomised trial (n=569) included cloth masks. This trial found ILI rates were 13 times higher in Vietnamese hospital workers allocated to cloth masks compared to medical/surgical masks, RR 13.25, (95%CI 1.74 to 100.97) and over three times higher when compared to no masks,* RR 3.49 (95%CI 1.00 to 12.17). 4 This is potentially because the masks start to lose effectiveness as soon as you put them on. DIY cloth masks soon become waterlogged with condensation, and then when you breath you push out aerosolised drops. https://www.ijic.info/article/view/10788 https://www.ijic.info/article/view/10788 > This study was conducted to check the efficacy of face masks in limiting bacterial dispersal when worn continuously in Operation Theater. A comparison was done to find out difference between fabric and two ply disposable masks. The first sample was collected prior to wearing the mask, using cough plate method holding a blood agar plate approximately 10 -12 centimeters away from the mouth. the personnel were asked to produce “ahh” phonation. Participants were then asked to don the face mask, continue routine work and report to the study center located inside the theater for further sample collections at designated intervals of 30, 60, 90, 120 and 150 minutes after wearing the fabric mask made of cotton. the study was replicated on immediate next day using two ply disposable mask keeping all the other conditions and personnel exactly the same. Bacterial counts before wearing the mask were 5.36±4.38 and 5.7±2.99 on day 1 and day 2 of study. Bacterial counts were 0.96±1.06 (P<0.001) and 0.7±0.87 (P<0.001) at 30 min; 2.33±1.42 (P<0.001) and 2.36±1.03 (P<0.001) at 60 min; 3.23±1.54 (P=0.007) and 4.16±1.78 (P=0.011) at 90 min; 5.63±4.02 (P=0.67) and 4.9±1.98 (P=0.161) at 120 min and 7.03±4.45 (P=0.019) and 5.6±2.21 (P=0.951) at 150min respectively for fabric and two ply disposable mask. Counts were near pre-wear level in about two hours irrespective of the type of mask. There was no significant difference between cotton fabric and two ply disposable masks. Face masks significantly decreased bacterial dispersal initially but became almost ineffective after two hours of use. My point is that we don't have the evidence to say whether masks work or not. You posting links to arstechnica and un-peer-reviewed pre-prints supports my point, doesn't it? If we had a Cochrane Collaboration meta analysis saying masks worked everyone would be posting that.
- misanthropian00 6y ago
  More emphasis on better masks that actually might prevent aerosol transmission and less emphasis on 6 foot distancing because such things matter little under aerosol conditions where air flow patterns dominate transmission. Also much more emphasis on outdoor vs indoor activities. So no it is not really the same guidance.
  - CogentHedgehog 6y ago
    Your claims do not reflect what the article and the evidence it cites show. To quote: > Cowling told me that it’s better to call these “short-range aerosols,” as that communicates the nature of the threat more accurately: Most of these particles are concentrated around the infected person, but, under the right circumstances, they can accumulate and get around. This is the precise opposite of your claim that 6 foot distancing would "matter little under aerosol conditions where air flow patterns dominate transmission." AT NO POINT does the article indicate that droplets are irrelevant. We know they are the key factor in person-to-person transmission. But we also now have evidence that short-range aerosols also play a role, especially in superspreading events. The evidence is VERY clear that risks are highest in close proximity to infected individuals. I would encourage you to take another look at the article and read closely.
    - misanthropian00 6y ago
      Well first of all there is little evidence on both sides of the argument here. There isn't much evidence in favor of aerosol transmission and there isn't much evidence against it either. I would hope that more research can be done on this matter. Perhaps I worded my statement poorly. Let me try to be more precise about the idea I was trying to express. If COVID really is more aerosol infectious than we have been assuming then the 6 foot distancing would matter much less in comparison because if a cloud of infectious COVID droplets is whirling in the air currents that effect will tend to dominate in the sense that your exact location relative to the COVID+ source is no longer a direct causal factor. Yes of course being farther away makes it less likely that you will be in the path of a relatively short range aerosol cloud but the important thing in that circumstance is not to be in its path and just being farther away in the same room may not be enough to avoid it. I don't deny that if someone with COVID coughs directly in your face which apparently was considered the dominant transmission vector at first you are also likely to be infected especially if you are not fully and properly masked and goggled. That must happen sometimes. Of course being at least 6 feet away from the closest person is a good thing. It is just the assumption that that is enough to keep people safe from COVID that should be questioned more. Anyway my quibble with your post was the part about the guidelines being the same. They aren't really. The difference may be slight, but it could be critical.
- graeme 6y ago
  Indeed. Governments have been slow to draw these lessons unfortunately. My local government (quebec) lets you remove masks at indoors events when seated.
  - CogentHedgehog 6y ago
    Governments are generally slow to change guidance when evidence is limited or ambiguous. The problem here is that while we have pretty solid evidence for short-distance aerosol transmission in some cases, it will take time to understand how BIG a factor it is. One thing that is easy to forget as a layperson: when it comes to public health, the government only has a limited ability to influence public behavior. Think of it as having a limited number of cards to play. So if they spend a card convincing people to wear masks indoors at events, then they can't spend it convincing people not to hold dinner parties (a common source of super-spreading events). Furthermore if the government emphasizes something that turns out to be ineffective, then they have even less ability to convince the public change their behavior in the future. This backlash gets worse if they appear to "change their mind" on something. Witness the backlash from health authorities shifting guidance on the importance of mask use in response to evidence of high pre-symptomatic/asymptomatic transmission of SARS-CoV-2. A huge part of the challenge for public health workers is figuring out what measures to emphasize and how to communicate it. I'm not saying the government responses are ideal: they almost never will be, especially with a new disease. But I can at least understand why they're slow to change their guidance.
    - graeme 6y ago
      This is true. However, they jumped on the deep cleaning guidance pretty quickly despite limited evidence.
credit_guy 6y ago
Wow, what a good article. Finally an article in a well respected publication that goes over the science of the Covid19 transmission, and appears to be non-partisan as well (what a tragedy that the approach to combat the disease has become a partisan issue). I really hope this article will, dare I say, "become viral". If it does, this article by itself could help save tens or hundreds of thousands of lives.
- martythemaniak 6y ago
  But it won't. The reason things became "partisan" is precisely because things like the article are useless and ineffective. You're assuming a shared reality that doesn't exist.
  - happytoexplain 6y ago
    You could be a little more gracious, and write a bit about the counterargument in your head, rather than framing your opinion as a dismissive argument right away. Edit: There may be some confusion: When you say, "things like the article are useless and ineffective", are you saying it's useless in reducing infection, or useless in communicating the message of how to reduce infection?
  - Loughla 6y ago
    I can only assume you're being downvoted because you've confused the chicken and the egg. Partisan issues don't exist because articles like this are useless and ineffective. Partisan stances on this sort of thing is what makes people believe articles like this are useless. You have it backwards. I would absolutely agree, though, that there is no such thing as a cultural 'shared reality' anymore. That is the base of the problem. There are very, very few shared experiences, and a section of the population is not, seemingly, even interested in trying to understand someone else's viewpoint.
    - vladvasiliu 6y ago
      Not sure what GP's line of reasoning is, but I agree the point could be stated in a finer way, although I roughly agree with it. > Partisan issues don't exist because articles like this are useless and ineffective. Partisan stances on this sort of thing is what makes people believe articles like this are useless. You have it backwards. I don't know. Is it really backwards? I can see how it could be argued that partisan stances spread as a consequence of people having short attention spans and preferring short, context-less flamewars on twitter or other social media instead of reading long-form articles like this one and developing their own thoughts on issues. Therefore it could be argued that, since people didn't pay (much) attention to articles like this to begin with, "they are useless and ineffective". It might actually be a self-reinforcing situation, though...
j_walter 6y ago
My company took steps to address this months ago. The re-circulation rate was set to zero so all air is fresh make up air from outside. This has significantly increased our cooling bill since it's summer, but it was something that we felt important even though there hasn't been much science to back it up. We also have a UV system hooked up to our system, but this has been installed for the last 2-3 years now.
- pfdietz 6y ago
  I wonder if air-to-air heat exchangers could address that cost issue.
  - masklinn 6y ago
    Surely all industrial / professional HVAC get installed with HRV and the loss here is going from the "100% efficient" recirc to HRV, no?
    - j_walter 6y ago
      Not all if it isn't designed that way (ours isn't because we never plan to not use recirc). The loss isn't actually that much and since we are using low temp cooling water to cool the air and we have a significant amount of that on site already we barely notice (still a cost though).
      - adrr 6y ago
        How old is your building? New construction is so weather sealed and lacks fresh air leaks to meet air quality standards. Pretty sure whatever standard to get a green rating on a building requires outside air to be mixed in and due to efficiency requirements there has to be heat exchanger.
        j_walter 6y ago
        25 years...but we also have the ability to open outside dampers on our return air chases to output all air if needed.
unclesaamm 6y ago
One key result of this evidence is that we should take all the money going into deep cleaning, and spend it on higher quality masks for everyone. Also perhaps makeshift ventilation systems (being careful not to replicate that Hong Kong restaurant) or outdoor tents where feasible.
- beamatronic 6y ago
  What was the restaurant doing wrong? Was it recirculating indoor air? Or was it actually exchanging the air? Replacing indoor air with fresh air from outside.
  - unclesaamm 6y ago
    The article links to the study. The issue was more than certain people sat downwind of others indoors, rather than where the air came from. Let me know if you read a different conclusion from it.
    - beamatronic 6y ago
      Now I’m really curious. How does one exchange indoor air safely?
  - deleted 6y ago
    [deleted]
  - felbane 6y ago
    As I understand it, the restaurant had an air conditioner in front of a table, and an infected but asymptomatic person was breathing into the airstream which was then circulated to infect anyone downwind of the a/c.
- doliveira 6y ago
  I was under the impression that the aerosol route was just common knowledge, but last week my state government (in Brazil) was doing deep cleaning in schools that have been closed for like 100 days. Yeah, good thing you're deep cleaning probably the last place on earth with no coronavirus! Now we'll only have problems if people want to breath in there... Such a stupid security theater.
ianpenney 6y ago
https://www3.nhk.or.jp/nhkworld/en/news/ataglance/855/ https://www3.nhk.or.jp/nhkworld/en/news/ataglance/855/ From April, Japan has been on top of this for a little while. Impressive science imho.
- sukilot 6y ago
  And yet Japanese government declared victory and campaigned against protective measures leading to a massive re-ourbreak, "for the economy"
  - addHocker 6y ago
    Those who pay, get to set the agenda. And its hard to convince a CEO who thinks money can move heaven and earth, that his influence should be limited by biology and physics.
  - thiagocesar 6y ago
    Japan has some really impressive universities and, as a rich country, is able to nurture all sorts of talent. The Japanese ruling party is a bunch of old people from a few traditional families mixed with some new faces. It’s very unfortunate how little these two worlds (talented people and politicians) collide.
KoftaBob 6y ago
This comes to mind every time I see a company/business emphasize how much priority they're putting on keeping people safe, and then only speaking about disinfecting every surface throughout the day. While it doesn't hurt to keep surfaces clean, we continue to see evidence that the majority of cases have come from airborne spread in an enclosed environment with poor ventilation. If there's any lasting change to building environments that comes out of this, I think it should be an overhaul of building ventilation codes to require/heavily incentivize systems that replace air rather than circulate it.
- lostapathy 6y ago
  Because wiping high-contact surfaces a few times a day is cheap, easy to do, and highly visible. And, hopefully, an easy extension of nightly cleaning that was already happening. Reworking your HVAC system to provide better circulation, filtration, and/or more fresh air is expensive, often an ongoing cost, and probably invisible to the end customer. I guess you could say it's well-intentioned virtue signaling.
tgb 6y ago
One problem is that no one seems to know that AC systems recirculate air. I literally can't get people to believe me when I tell them this. When buying a window unit recently, some models had the ability to incorporate fresh outside air but the cheaper ones didn't. My home is leaky enough that I worry more about keeping outside air out rather than in, though.
- bluGill 6y ago
  The ones that bring in outside air (that I have seen) just let a little outside air in. Most of the air is still recirculated, but there is a tiny hole that opens to let some air in.
- sukilot 6y ago
  Do people not use the recirc switch in their car?
  - tgb 6y ago
    I think this actually makes it more understandable. If recirc is a special mode you have to activate in your car's AC, then it's reasonable to assume it's not the default mode for your house AC too. Since they never had a 'recirc' button to press at home, they'd assume it doesn't recirculate. Reasonable, but inaccurate.
- stx 6y ago
  Unless someone who has it is inside your home I don't think you need to worry about the air recirculating. I agree though its amazing that people don't understand how this works.
graeme 6y ago
If anyone is in an indoor environment and wants to gauge risk, a portable co2 meter can be had for about $100-$150. Cod2 is a good proxy for indoor pollutants/air exchange, and I’m assuming it is a good proxy for aerosols too. I use one of these, you can use a portable battery to power it. https://www.amazon.com/AutoPilot-APCEMDL-Desktop-Data-Storage/dp/B07JDJP4HH/ref=sr_1_15?dchild=1&keywords=Co2+meter+autopilot&qid=1596467296&sr=8-15 https://www.amazon.com/AutoPilot-APCEMDL-Desktop-Data-Storag...
- klysm 6y ago
  It seems to be an even better proxy for aerosol risk compared to general circulation because co2 is coming from lungs - I might make myself a wearable logger
- ketamine__ 6y ago
  We're constantly filling the rooms we occupy with aerosols from our mouths. How will this help?
  - function_seven 6y ago
    Because we’re also constantly filling rooms with the CO2 that we exhale. The CO2 meter acts as a proxy for how much exhaled “stuff” is lingering about. So if your CO2 meter shows that the room is at ~400ppm [:’(], rather than 800 or 1000, then you can deduce that the room is well ventilated. I’m other words, whatever ventilation removed the excess CO2 most likely also removed the aerosols at the same time.
    - driverdan 6y ago
      Considering atmospheric CO2 levels are around 400ppm you're not going to keep it that low indoors unless it's full of open windows.
      - graeme 6y ago
        Yup. I have all of my windows open right now, it’s summer. Co2 tends to be around 500. Even outdoor city air in my location is more like 450, though of course my meter could be biased high.
R0b0t1 6y ago
This is a good article. I work at a biotech company that studies virus transmission and helps others study it. It was clear from the very beginning that transmission was airborne. Why would it not be? That the WHO and some doctors were assuming it was not seriously damages their credibility as healthcare professionals. Current events should lead people to seriously question deference given to doctors. They need to be held accountable for their actions and must be made to listen to professionals in other fields.
- aantix 6y ago
  Why wasn't there a large spike with the recent protests in the participating demographic? https://www.forbes.com/sites/tommybeer/2020/07/01/research-determines-protests-did-not-cause-spike-in-coronavirus-cases/ https://www.forbes.com/sites/tommybeer/2020/07/01/research-d... The chants "no justice, no peace"? "I can't breath"? Those were clear chants. Everyone breathing on each other while chanting. Unencumbered by a mask.
  - squeaky-clean 6y ago
    > Unencumbered by a mask. Got a source on this? From the protests I've been attending, I'd say mask usage is easily at 99% of attendees. Everyone pictured in your linked article also has a mask, at least 10% have full masks and face shields.
    - derg 6y ago
      hell at the ones I went to there were roving groups of people handing out masks and gloves (more masks than gloves and the masks came directly from the box), hand sanitizer, and water. it was a sight to see honestly and very heartening bit of community and mutual aid.
  - machello13 6y ago
    That's only a single paper, hardly conclusive. But also: > Unencumbered by a mask. The picture at the beginning of the article you linked shows every protester wearing a mask.
kenjackson 6y ago
There is a weird disconnect. Everyone seems to acknowledge the most likely way to transmit COVID is via droplets when indoor. Yet, there is little discussion about ventilation. Maybe people felt like there was less they could do?
- KoftaBob 6y ago
  If I had to guess, it's because sanitizing surfaces all day is cheaper/easier than upgrading the ventilation system.
- obelos 6y ago
  I think this is it. Everyone's painting the roses red because spritzing some sanitizer on every surface costs a minuscule fraction of the massive revamping of indoor climate that's actually required to reduce risk.
- ghaff 6y ago
  >Maybe people felt like there was less they could do? Probably mostly that plus a lot of the attention focused on transmission by touch early on. The last event I went to in March there was no handshaking, cleaning of surfaces, etc. But no masks or distancing. But, yeah, taking additional care to clean surfaces is pretty easy and cheap. Completely redoing ventilation is going to be pretty much impossible in a lot of situations.
- ehnto 6y ago
  Gyms and restaurants have had their air conditioning off in Aus. Israel turned off their bus air conditioning. This isn't breaking news but I suspect it would be a new angle to the media rhetoric for a few countries and media outlets.
  - Bootwizard 6y ago
    It's the middle of summer in the US so that's not going to go over well here. Just another thing for Karens to yell about and get on the news.
jennyyang 6y ago
After this pandemic, doctors and scientists are going to have to come up with more media-friendly terms from now on. The problem is that "airborne droplets" and "airborne" sound too similar and it's very hard for regular people to understand what that means. "Airborne droplets" means that viruses need saliva to transmit between people. "Airborne" means that the virus only needs dust particles to transmit to other people. Measles is airborne transmission, which means that if someone with measles enters a room, that room can be infectious for 12+ hours because viruses will be infectious in the dust. If someone with coronavirus sneezes in a room, the large heavy droplets will quickly fall to the ground. If you breathe in the droplets then you can catch the virus, but these only stay in the air for seconds. However, there are microdroplets which stay in the air for 30+ minutes depending on the air currents. So there is a distinction between them. If coronavirus were truly airborne, then we would all need to wear masks all the time, even when no one is around. No where would be safe and we would have to implement extremely strict lockdowns. But the fact that scientists and doctors have chosen to use the term "airborne" in both have made it extremely confusing and given how quickly information and misinformation is disseminated these days, they need to choose terms with care from now on.
- enraged_camel 6y ago
  The article addresses this midway through. The problem is that even the experts haven't really agreed on terminology. They need to do that first before they can hope to inform the public. :)
  - mc32 6y ago
    So why talk about HVAC systems ? Context: >” by 10 bottles of hand sanitizer without a word on ventilation—whether it was opening windows, employing upgraded filters in its HVAC systems, or using portable HEPA filters. It seems baffling that despite mounting evidence of its importance, we are stuck practicing hygiene theater...”
    - enraged_camel 6y ago
      Sorry, what do you mean?
deleted 6y ago
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misanthropian00 6y ago
Yes it's a well written article by a clearly intelligent author who did his homework and knows his sources and of course we should never have ruled out short range aerosols. It's ridiculous. I think it only happened because so many people just believe whatever authorities like the CDC and WHO tell them without any critical reasoning applied. If these health agencies had not effectively ruled out the possibility afaik without any supporting evidence maybe there would have been more research to figure out droplet sizes and travel paths under various airflow conditions. Currently everyone seems to just want to make assumptions and stick to them, but that isn't science even if you call yourself a scientist. Maybe also N95 masks would have been considered essential not only just to health care workers and maybe more effort might have been made to supply some to the general population. Currently 3M for instance voluntarily stopped selling their masks except to hospitals and speaking of those masks there is also not enough research on effective ways of decontaminating those masks without reducing their filtration effectiveness so that they can be reused more often and so that more can be made available to the public instead of effectively making them hospital only.
ColanR 6y ago
We probably aren't hearing about it because it's something we have less ability to protect against. I remember a popular comment here a while back mentioning that epidemeologists' job is partly public relations, trying to figure out what they can tell the general public that will minimize the viral spread. Making sure everyone wears masks will, at the scale of the general population, reduce the infection rate by some noticable percent. It's also something everyone can do, and it gives everyone a sense of control over the situation - enough of a sense, at least, to prevent chaos. Talking about airborne transmission, though? The kind of masks that can protect against that are hard to come by. Not to mention that the virus could enter via the fluid of the eyes (not trying to add conspiracy here, just trying to make a point about the difficult reality of preventing infection [0]). Bio-rated goggles and N95+ rated masks are more than we can expect from a public that's making face masks out of bandannas. I think we're seeing very pragmatic statements being made, that are tailored to a public that can't enter full biohazard mode and need to not panic. [0] https://www.biorxiv.org/content/10.1101/2020.05.09.085613v2 https://www.biorxiv.org/content/10.1101/2020.05.09.085613v2
- sigstoat 6y ago
  > Talking about airborne transmission, though? The kind of masks that can protect against that are hard to come by. Not to mention that the virus could enter via the fluid of the eyes (not trying to add conspiracy here, just trying to make a point about the difficult reality of preventing infection [0]). Bio-rated goggles and N95+ rated masks are more than we can expect from a public that's making face masks out of bandannas. plenty of evidence that even a little bit of protective gear helps. it isn't a matter of hazmat-suit-or-GTFO.
  - ColanR 6y ago
    > Making sure everyone wears masks will, at the scale of the general population, reduce the infection rate by some noticable percent. I said that.
  - ghaff 6y ago
    I think that's what the parent was saying. The widespread wearing of just about any face covering seems to help on net even if it's probably >50% about protecting other people. Even if higher-level protective gear were readily available, most people wouldn't wear for any length of time and it wouldn't be fitted properly. So just wear something seems to be the most reasonable advice for the general population.
sigstoat 6y ago
i wish target and home depot would stop making us wait in line while they futz about wiping things down. it's been clear that time spent in line with other people is a bigger concern than the possibility that something is lingering on the barcode scanner and will be transferred onto my box of nails, or bananas.
scythe 6y ago
One issue is that we seem to have an all-or-nothing view of infection. People think that either a virus gets in your nose and you get sick, or it doesn't and you're fine. This extends to thinking that either there is a risk or there isn't, which motivates incorrect anti-mask arguments. In reality, the probability of infection varies continuously with the degree of exposure, and the minimal infective dose might be prevented even if not all viral particles can be blocked. https://en.wikipedia.org/wiki/Minimal_infective_dose https://en.wikipedia.org/wiki/Minimal_infective_dose With airborne transmission, it is practically impossible to reduce the transmission probability to zero in many situations, and we have overlooked the value of finite improvements. However, the circumstantial evidence suggests that, since super-spreader events are correlated with apparently high airborne concentrations of viral particles, that reducing the duration and intensity of exposure may yield significant benefits even if inhaled air cannot be made completely free of virions.
- deleted 6y ago
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- acqq 6y ago
  Exactly, that "all or nothing" is the main problem in in how most of the people think about the whole topic. I've read one work that gave the very simple estimates: if the infected person wears the surgical mask it will emit 50% less in the air, and if the non-infected person wears the surgical mask that person will get 60% of what's in the air. But combined, that means that the non-infected person will get around only 30% of what it would get when nobody would wear a mask. Which seems to be way too little for personal "full" protection, but looking more globally: If the R factor (reproduction number) is 2.7 with no measures, and if everybody wears a mask and other limitations are respected (physical distancing, limiting the number or people in the closed spaces, ventilation, etc.), all together it can result in the R factor being reduced to less than 1: With the known no-measures factor 2.7 we have exponential growth. With the factor under 1, we have a steady decay in the number of infected people. There we also "just" have to reduce that factor to 30% of the no-measures one. It's not so easy as some people spread to many, and a lot already don't pass the virus to others. That's why groups of people near each other change everything too much. But just by maintaining the factor under 1 (the lower the better) we guarantee that the relative number of infected around us will be always be smaller and smaller, and that's can be more than enough for the population as the whole. That's why wearing the masks and any additional good measures together do help, even if every measure, evaluated alone, for only one person, "doesn't protect" enough. So it is not just either 0 or 100%, but everything in between: not everybody has to use the same protection that the medical workers have to to improve the chances for everybody. But everybody should do it. One person who's actually infected and not wearing its mask changes the number of viruses passed to anybody in its vicinity from 30% to 60%, when all the rest wear the masks, or to 0 to somebody who's also not wearing the mask. From the starting 50% and 60% of masks "working" we get all the other outcomes too. And the same is valid for testing. Rapid wide scale cheap testing to identify who should enter the building doesn't have to be as good as PCR tests to still give us immense benefits, if we have it and use it. We just have to be clear that we want it, and that we know now it's not about "either 0 or 100%." Also, the pictures (and the video) explaining much more than many words: "Face coverings and mask to minimise droplet dispersion and aerosolisation: a video case study" https://thorax.bmj.com/content/early/2020/07/24/thoraxjnl-2020-215748 https://thorax.bmj.com/content/early/2020/07/24/thoraxjnl-20...
MiguelVieira 6y ago
When I look at this heat map of recent cases per capita in the US https://globalepidemics.org/key-metrics-for-covid-suppression/ https://globalepidemics.org/key-metrics-for-covid-suppressio... the first thing I see is hot spots all across the southeast and desert southwest. These places have widely varying governments and cultures, but the one thing they do have in common right now is: they're hot. My suspicion is that many of the outbreaks we've seen recently are caused by people from different households congregating indoors in buildings with air conditioning and closed windows. The article mentions this, but I rarely here it talked about on the news: "The importance of aerosols may even help explain why the disease is now exploding in the southern United States, where people often go into air-conditioned spaces to avoid the sweltering heat."
- sp332 6y ago
  And this might switch in winter, as people in the south get outside more and the north buttons up for the cold.
- milesvp 6y ago
  This is something I currently speculate too. Hotter states really benefited from AC allowing people to live there comfortably. I think it might show us what’s coming as people move indoors in colder months elsewhere. It’s getting harder and harder to stay away from people from a purely psychological standpoint, and I think fall is going to get bad in the PNW as people congregate indoors to stay out of the wet and cold.
- Vysero 6y ago
  Ben Shapiro has been saying that for months..
js2 6y ago
A couple other articles I've read in the last few days also cover this topic: Yes, the Coronavirus Is in the Air > Transmission through aerosols matters — and probably a lot more than we’ve been able to prove yet. ... > I am a civil and environmental engineer who studies how viruses and bacteria spread through the air — as well as one of the 239 scientists who signed an open letter in late June pressing the W.H.O. to consider the risk of airborne transmission more seriously. https://www.nytimes.com/2020/07/30/opinion/coronavirus-aerosols.html https://www.nytimes.com/2020/07/30/opinion/coronavirus-aeros... Aboard the Diamond Princess, a Case Study in Aerosol Transmission > A computer model of the cruise-ship outbreak found that the virus spread most readily in microscopic droplets light enough to linger in the air. https://www.nytimes.com/2020/07/30/health/diamond-princess-coronavirus-aerosol.html https://www.nytimes.com/2020/07/30/health/diamond-princess-c... And here's an article from two weeks ago that goes into some depth on superspreading events: https://www.washingtonpost.com/health/2020/07/18/coronavirus-superspreading-events-drive-pandemic/ https://www.washingtonpost.com/health/2020/07/18/coronavirus... > He believes ventilation may also be to blame for a case involving a young man from China’s Hunan province, who sat in the back of a bus but ended up infecting seven others in various areas of the vehicle and then two more on a second minibus he hopped onto next. Li interviewed the patient, driver, passengers and reviewed video footage and found it odd that few of those who became infected were nearby. In fact, at least one passenger who fell ill was as far away as possible at the front of the bus — 31 feet away — from the coronavirus-positive man. […] In the case of the Hunan man who transmitted the virus while riding two buses, Li said that “amazingly” after that four-hour window of infectivity, he is not known to have infected anyone else at all.
nabla9 6y ago
Just look at the list of people who signed the letter. They are experts in their field but they don't have the expertise to consider the whole picture. It's possible, that there is some airborne transmission besides droplets, but there is no evidence that it's significant transmission route. To get infected you need big enough dose of virus at once. Just some dry floating particles in the air is not enough.
thinkingemote 6y ago
in the UK the LNER train company highlights ventilation amongst other things, but the ventilation bit I found suprising when I encountered it. https://www.lner.co.uk/travel-information/lets-travel-together-safely/ https://www.lner.co.uk/travel-information/lets-travel-togeth... " Our onboard ventilation systems are providing a continuing supply of fresh air which is cycled every 6 minutes limiting droplet transmission between passengers." With the graphics implying that ventilation is spatially limited.
- tialaramex 6y ago
  The closest to air-conditioning possible in trains like LNER's is more similar to individual window units (except mounted in the ceiling) than the integrated systems in larger homes or offices. LNER operates two types of multiple-unit from the same family (a conventional EMU and then a bi-modal hack of that concept because the Tories don't want to spend money electrifying more of the railway), and then an older loco-hauled passenger service where a type 91 is pulling and there's a train of mostly passive passenger stock behind it. In both these designs there is electricity available, to run the air conditioning units, but it's not practical to pump air around the train so they don't. The air in your part of the train will get recirculated by the fans that make the air conditioning unit work, so I'd expect that if you spent an hour on a train four seats from an infectious person there's a decent chance you'll be infected. But air from other carriages isn't recirculated into yours at more than negligible level. Because these are mostly doing intercity journeys (thus fewer stops, and perhaps dwelling for longer at each) even the newer EMUs were not designed as a single huge tube like the modern Tube stuck or some local EMUs. So there's a "double airlock" partition between one carriage and the next which reduces noise and discomfort but makes getting on and off take a little longer. In this particular case it probably makes the train slightly safer to use.
eqdw 6y ago
Talking about airborne transmission would make it too obvious that masks are pointless security theatre. Can't have that
DoofusOfDeath 6y ago
The article makes an excellent argument for the plausibility of indoor airflows being a major transmission vector. But I didn't see anything about ongoing research to quantify the transmission risks posed by aerosols vs. other transmission mechanisms. (Maybe I missed it?) It's hard to make policy recommendations regarding aerosols if (a) we're not really sure how big a risk factor they pose and (b) the mitigations would be very expensive.
whydoyoucare 6y ago
I think we can't talk about it because there is no agreement on terms, modes of transmission, etc. and public policy cannot be based on ambiguous terms (though it can be based on imperfect data).
lurkmurk 6y ago
The amount of unknown and disagreement after all this time and money spent is a big failure of science. Laymen have a unique peak into how science works day to day, which might be good or bad depending on how you see it.
mensetmanusman 6y ago
I am still shocked: months after research has shown that SARS-CoV-2 is airborne stable in aerosol form for over 3 hours, we still aren’t telling the public that room air purifiers are a ‘good thing’ (for making indoor air like outdoor air - in regards to virion density per cubic air volume) The filter technology is essentially the same as in the N95, orders of magnitude more effective than cloth masks. Put these indoors, multiple per classroom/working space to help the air refresh in sub 5 minute intervals.
- ogre_codes 6y ago
  My wife works in a doctors office which has stayed open through the pandemic. She sees a few people a day in a small room. The very first thing she did after the pandemic hit the US, was buy an air purifier and she runs it continually. I'm quite surprised that they aren't more common in medical offices in general. The benefits of the air filter are cumulative with other protections—particles caught by the filter can't bypass the mask. Filters should be mandatory in any enclosed room, the fact that they don't even talk about them as part of the discussion about schools and businesses opening is mind boggling to me.
  - yellow_postit 6y ago
    Expect we will see a repeat of the bungled rush for air purifiers as we did with ventilators.
    - ogre_codes 6y ago
      As with the ventilators, a bungled rush for them is better than not using them at all. Obviously if they had a more ordered distribution it would be better, but any movement in the correct direction would be an improvement.
    - mensetmanusman 6y ago
      Here would could at least prioritize schools? Ventilators was only bungled because it turned out to be the wrong therapy... air purifiers is a win win win
cblconfederate 6y ago
At the beginning of the epidemic, joe rogan hosted M.Osterholm for an interview where he warned about a lot of the things to come: the rapid spread, the small effect of washing hands or masks, the airborne spread etc. It's sad that the epidemic seems to have turned worse than most ppl assume it would.
mensetmanusman 6y ago
I am sympathetic to what the WHO did here, they realize that the average person is going to be extremely fearful when they realize that stagnant air could contain virion particles hours after being sneezed in (which is what the data show). They should have erred on telling people, because then we would have had months to ramp up room air purifiers before school starts... (I have been saying this for months, and am surprised by the lack of scientific leadership in ‘science’ organizations).
- klysm 6y ago
  Why should the WHO not incite fear if the fear is entirely rational and justified? People not being afraid enough is exactly how people die.
prof-dr-ir 6y ago
I would like to make a small point about the letter signed by "hundreds of scientists around the world". According to the NY Times there were in fact 239 signatories, which coincidentally is almost the same number as the "253 ... scientists from 44 nations" warning of the dangers of electromagnetic radiation (!) that can be found at https://emfscientist.org/ https://emfscientist.org/ . If you trust one, do you trust the other also? Regardless of the merits of the rest of the article, I would caution against trusting a claim just because two hundred odd scientists from all sorts of disciplines were willing to sign an open letter. Science is not a democracy.
- briandear 6y ago
  The “appeal to authority” is also used to sell toothbrushes. I agree that it’s foolish to trust an article or “fact” because 9 out of 10 doctors agree. I am very interested in why that 10th doctor didn’t agree..
CogentHedgehog 6y ago
There's one key paragraph buried in the article that will help a lot of people: > However, to date, there is also no evidence of truly long-range transmission of COVID-19, or any pattern of spread like that of measles. Screaming “it’s airborne!” can give the wrong impression to an already weary and panicked public, and that’s one reason that some public-health specialists have been understandably wary of the term, sometimes even if they agreed aerosol transmission was possible. Cowling told me that it’s better to call these “short-range aerosols,” as that communicates the nature of the threat more accurately: Most of these particles are concentrated around the infected person, but, under the right circumstances, they can accumulate and get around. Translation: people can get infected further away than with larger droplets -- especially in stuffy, enclosed environments -- but distance still reduces the risks.
- DoingIsLearning 6y ago
  > people can get infected further away than with larger droplets Minor nitpick, you can think of aerosol transmission as plume of virus particles. Technically you can get infected long after the carrier has left a closed room, at which point the concept of being "further away" stops applying.
  - CogentHedgehog 6y ago
    That's true, in this case "further away" is a 4-dimensional distance vector (it includes time). :D
jsonbourne 6y ago
There is this startup which came up with the solution for the airborne problem. https://yourstory.com/2020/07/startup-bharat-kanpur-crestkiting-retail-air-purification https://yourstory.com/2020/07/startup-bharat-kanpur-crestkit...
rurban 6y ago
There are no receptors in the mouth, only nose and eyes. So the mouth does not need to be protected passively, the only problem is that the mouth is the only actor to spread the virus effectively.

301 points by KoftaBob 6y ago

Short-distance aerosol transmission changes things a bit: * Social distancing isn't enough to guarantee safety in indoors spaces: bad news for bars, clubs, gyms, concerts, and restaurants * Outdoors spaces are probably safer than we previously thought * Indoor mask-wearing becomes CRITICAL in public spaces * Indoor ventilation becomes extra important, using fresh air from outside or filtered/UV-sanitized air * Indoor air purifiers with HEPA ratings or UV sterilizer features may become valuable But the same overall guidance still applies: avoid crowds, wear a mask, keep your distance, outdoors activities are safer than indoors activities

DanBC 6y ago
> Indoor mask-wearing becomes CRITICAL in public spaces Mask wearing provides minimal benefits against droplet transmission, but they do nothing at all for small droplet aerosol transmission.
- misanthropian00 6y ago
  What do you consider a small droplet? The masks are tested with 0.3 micron droplets. Do you have a source?
- keenmaster 6y ago
  Studies have found that a combination of multi-layered cotton and chiffon/silk masks prevents intake of both large and small droplets. Silk/chiffon act magnetically on smaller particles to keep you from breathing them in, while the thick cotton layers stop large droplets. The aggregate effect is similar to N95, but more washable and reusable. It blows my mind that this was discovered a couple months ago and the government still hasn’t funded the mass production of such masks. After I read the study, I bought 2 masks on Etsy.com: a multilayered cotton mask and a silk mask. I wear both when I go out. What’s great is that I don’t just protect others from me, but I also protect myself from others to a large extent (as opposed to just wearing the cotton mask). As for comfort, silk is light and thin, so it doesn’t add any noticeable discomfort on top of the cotton mask. https://news.uchicago.edu/story/homemade-masks-made-silk-and-cotton-may-boost-protection https://news.uchicago.edu/story/homemade-masks-made-silk-and... Note: Newer studies have found that even just a thick cotton mask does somewhat protect you (not as much as cotton + silk of course, but they protect others from you quite effectively). You still need to be careful, generally avoid indoor environments with strangers, and socially distance. Not that that disclaimer is super necessary, because other studies have found that masks do not make people behave more recklessly :) If anything, they make you more careful and acutely aware of COVID risks.
  - DanBC 6y ago
    > Newer studies have found that even just a thick cotton mask does somewhat protect you No they haven't. If the effect of masks was so strong it would be easy to find that when we do trials. We've done the trials and we struggle to see the effect. Once we drop down the quality requirements we start to see an effect, but even that is mild. https://www.thelancet.com/action/showPdf?pii=S0140-6736%2820%2931142-9 https://www.thelancet.com/action/showPdf?pii=S0140-6736%2820... > Although direct evidence is limited, the optimum use of face masks, in particular N95 or similar respirators in health-care settings and 12–16-layer cotton or surgical masks in the community, could depend on contextual factors; action is needed at all levels to address the paucity of better evidence. Eye protection might provide additional benefits. Globally collaborative and well conducted studies, including randomised trials, of different personal protective strategies are needed regardless of the challenges, but this systematic appraisal of currently best available evidence could be considered to inform interim guidance There's no way to spin phrases like "direct evidence is limited" and "paucity of evidence" to mean "we've got good quality evidence that shows an effect".
- CogentHedgehog 6y ago
  That's actually the opposite of what the evidence shows. Masks - even crappy ones, with poor mask protocol - dramatically cut infections https://arstechnica.com/science/2020/06/modeling-the-impact-of-face-masks-on-the-covid-19-pandemic/ https://arstechnica.com/science/2020/06/modeling-the-impact-... Citation: https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818 https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818 Remember: even if a mask doesn't effectively filter out very small particles, it still restricts the velocity of air passing through it. This means aerosolized particles will not travel as far.
  - DanBC 6y ago
    About your arstechnica link: if masks don't work all that effectively you need huge numbers of people to wear them to prevent a single infection. https://www.fhi.no/globalassets/dokumenterfiler/rapporter/2020/should-individuals-in-the-community-without-respiratory-symptoms-wear-facemasks-to-reduce-the-spread-of-covid-19-report-2020.pdf https://www.fhi.no/globalassets/dokumenterfiler/rapporter/20... > Non-medical facemasks include a variety of products. There is no reliable evidence of the effectiveness of non-medical facemasks in community settings. There is likely to be substantial variation in effectiveness between products. However, there is only limited evidence from laboratory studies of potential differences in effectiveness when different products are used in the community. > Given the low prevalence of COVID-19 currently, even if facemasks are assumed to be effective, the difference in infection rates between using facemasks and not using facemasks would be small.Assuming that 20% of people infectious with SARS-CoV-2 do not have symptoms,and assuming a risk reduction of 40% for wearing facemask, 200000 people would need to wear facemasks to prevent one new infection per week in the current epide-miological situation. Here's all the science: we don't know if masks work or not. https://www.cebm.net/covid-19/masking-lack-of-evidence-with-politics/ https://www.cebm.net/covid-19/masking-lack-of-evidence-with-... They have a plausible mechanism of action, but they also have plausible mechanisms of harm. The above link includes one trial where they appeared to be harmful: > It is debatable whether any of these results could be applied to the transmission of SARs-CoV-2. Only one randomised trial (n=569) included cloth masks. This trial found ILI rates were 13 times higher in Vietnamese hospital workers allocated to cloth masks compared to medical/surgical masks, RR 13.25, (95%CI 1.74 to 100.97) and over three times higher when compared to no masks,* RR 3.49 (95%CI 1.00 to 12.17). 4 This is potentially because the masks start to lose effectiveness as soon as you put them on. DIY cloth masks soon become waterlogged with condensation, and then when you breath you push out aerosolised drops. https://www.ijic.info/article/view/10788 https://www.ijic.info/article/view/10788 > This study was conducted to check the efficacy of face masks in limiting bacterial dispersal when worn continuously in Operation Theater. A comparison was done to find out difference between fabric and two ply disposable masks. The first sample was collected prior to wearing the mask, using cough plate method holding a blood agar plate approximately 10 -12 centimeters away from the mouth. the personnel were asked to produce “ahh” phonation. Participants were then asked to don the face mask, continue routine work and report to the study center located inside the theater for further sample collections at designated intervals of 30, 60, 90, 120 and 150 minutes after wearing the fabric mask made of cotton. the study was replicated on immediate next day using two ply disposable mask keeping all the other conditions and personnel exactly the same. Bacterial counts before wearing the mask were 5.36±4.38 and 5.7±2.99 on day 1 and day 2 of study. Bacterial counts were 0.96±1.06 (P<0.001) and 0.7±0.87 (P<0.001) at 30 min; 2.33±1.42 (P<0.001) and 2.36±1.03 (P<0.001) at 60 min; 3.23±1.54 (P=0.007) and 4.16±1.78 (P=0.011) at 90 min; 5.63±4.02 (P=0.67) and 4.9±1.98 (P=0.161) at 120 min and 7.03±4.45 (P=0.019) and 5.6±2.21 (P=0.951) at 150min respectively for fabric and two ply disposable mask. Counts were near pre-wear level in about two hours irrespective of the type of mask. There was no significant difference between cotton fabric and two ply disposable masks. Face masks significantly decreased bacterial dispersal initially but became almost ineffective after two hours of use. My point is that we don't have the evidence to say whether masks work or not. You posting links to arstechnica and un-peer-reviewed pre-prints supports my point, doesn't it? If we had a Cochrane Collaboration meta analysis saying masks worked everyone would be posting that.
misanthropian00 6y ago
More emphasis on better masks that actually might prevent aerosol transmission and less emphasis on 6 foot distancing because such things matter little under aerosol conditions where air flow patterns dominate transmission. Also much more emphasis on outdoor vs indoor activities. So no it is not really the same guidance.
- CogentHedgehog 6y ago
  Your claims do not reflect what the article and the evidence it cites show. To quote: > Cowling told me that it’s better to call these “short-range aerosols,” as that communicates the nature of the threat more accurately: Most of these particles are concentrated around the infected person, but, under the right circumstances, they can accumulate and get around. This is the precise opposite of your claim that 6 foot distancing would "matter little under aerosol conditions where air flow patterns dominate transmission." AT NO POINT does the article indicate that droplets are irrelevant. We know they are the key factor in person-to-person transmission. But we also now have evidence that short-range aerosols also play a role, especially in superspreading events. The evidence is VERY clear that risks are highest in close proximity to infected individuals. I would encourage you to take another look at the article and read closely.
  - misanthropian00 6y ago
    Well first of all there is little evidence on both sides of the argument here. There isn't much evidence in favor of aerosol transmission and there isn't much evidence against it either. I would hope that more research can be done on this matter. Perhaps I worded my statement poorly. Let me try to be more precise about the idea I was trying to express. If COVID really is more aerosol infectious than we have been assuming then the 6 foot distancing would matter much less in comparison because if a cloud of infectious COVID droplets is whirling in the air currents that effect will tend to dominate in the sense that your exact location relative to the COVID+ source is no longer a direct causal factor. Yes of course being farther away makes it less likely that you will be in the path of a relatively short range aerosol cloud but the important thing in that circumstance is not to be in its path and just being farther away in the same room may not be enough to avoid it. I don't deny that if someone with COVID coughs directly in your face which apparently was considered the dominant transmission vector at first you are also likely to be infected especially if you are not fully and properly masked and goggled. That must happen sometimes. Of course being at least 6 feet away from the closest person is a good thing. It is just the assumption that that is enough to keep people safe from COVID that should be questioned more. Anyway my quibble with your post was the part about the guidelines being the same. They aren't really. The difference may be slight, but it could be critical.
graeme 6y ago
Indeed. Governments have been slow to draw these lessons unfortunately. My local government (quebec) lets you remove masks at indoors events when seated.
- CogentHedgehog 6y ago
  Governments are generally slow to change guidance when evidence is limited or ambiguous. The problem here is that while we have pretty solid evidence for short-distance aerosol transmission in some cases, it will take time to understand how BIG a factor it is. One thing that is easy to forget as a layperson: when it comes to public health, the government only has a limited ability to influence public behavior. Think of it as having a limited number of cards to play. So if they spend a card convincing people to wear masks indoors at events, then they can't spend it convincing people not to hold dinner parties (a common source of super-spreading events). Furthermore if the government emphasizes something that turns out to be ineffective, then they have even less ability to convince the public change their behavior in the future. This backlash gets worse if they appear to "change their mind" on something. Witness the backlash from health authorities shifting guidance on the importance of mask use in response to evidence of high pre-symptomatic/asymptomatic transmission of SARS-CoV-2. A huge part of the challenge for public health workers is figuring out what measures to emphasize and how to communicate it. I'm not saying the government responses are ideal: they almost never will be, especially with a new disease. But I can at least understand why they're slow to change their guidance.
  - graeme 6y ago
    This is true. However, they jumped on the deep cleaning guidance pretty quickly despite limited evidence.

credit_guy 6y ago

Wow, what a good article. Finally an article in a well respected publication that goes over the science of the Covid19 transmission, and appears to be non-partisan as well (what a tragedy that the approach to combat the disease has become a partisan issue). I really hope this article will, dare I say, "become viral". If it does, this article by itself could help save tens or hundreds of thousands of lives.

martythemaniak 6y ago
But it won't. The reason things became "partisan" is precisely because things like the article are useless and ineffective. You're assuming a shared reality that doesn't exist.
- happytoexplain 6y ago
  You could be a little more gracious, and write a bit about the counterargument in your head, rather than framing your opinion as a dismissive argument right away. Edit: There may be some confusion: When you say, "things like the article are useless and ineffective", are you saying it's useless in reducing infection, or useless in communicating the message of how to reduce infection?
- Loughla 6y ago
  I can only assume you're being downvoted because you've confused the chicken and the egg. Partisan issues don't exist because articles like this are useless and ineffective. Partisan stances on this sort of thing is what makes people believe articles like this are useless. You have it backwards. I would absolutely agree, though, that there is no such thing as a cultural 'shared reality' anymore. That is the base of the problem. There are very, very few shared experiences, and a section of the population is not, seemingly, even interested in trying to understand someone else's viewpoint.
  - vladvasiliu 6y ago
    Not sure what GP's line of reasoning is, but I agree the point could be stated in a finer way, although I roughly agree with it. > Partisan issues don't exist because articles like this are useless and ineffective. Partisan stances on this sort of thing is what makes people believe articles like this are useless. You have it backwards. I don't know. Is it really backwards? I can see how it could be argued that partisan stances spread as a consequence of people having short attention spans and preferring short, context-less flamewars on twitter or other social media instead of reading long-form articles like this one and developing their own thoughts on issues. Therefore it could be argued that, since people didn't pay (much) attention to articles like this to begin with, "they are useless and ineffective". It might actually be a self-reinforcing situation, though...

j_walter 6y ago

My company took steps to address this months ago. The re-circulation rate was set to zero so all air is fresh make up air from outside. This has significantly increased our cooling bill since it's summer, but it was something that we felt important even though there hasn't been much science to back it up. We also have a UV system hooked up to our system, but this has been installed for the last 2-3 years now.

pfdietz 6y ago
I wonder if air-to-air heat exchangers could address that cost issue.
- masklinn 6y ago
  Surely all industrial / professional HVAC get installed with HRV and the loss here is going from the "100% efficient" recirc to HRV, no?
  - j_walter 6y ago
    Not all if it isn't designed that way (ours isn't because we never plan to not use recirc). The loss isn't actually that much and since we are using low temp cooling water to cool the air and we have a significant amount of that on site already we barely notice (still a cost though).
    - adrr 6y ago
      How old is your building? New construction is so weather sealed and lacks fresh air leaks to meet air quality standards. Pretty sure whatever standard to get a green rating on a building requires outside air to be mixed in and due to efficiency requirements there has to be heat exchanger.
      - j_walter 6y ago
        25 years...but we also have the ability to open outside dampers on our return air chases to output all air if needed.

unclesaamm 6y ago

One key result of this evidence is that we should take all the money going into deep cleaning, and spend it on higher quality masks for everyone. Also perhaps makeshift ventilation systems (being careful not to replicate that Hong Kong restaurant) or outdoor tents where feasible.

beamatronic 6y ago
What was the restaurant doing wrong? Was it recirculating indoor air? Or was it actually exchanging the air? Replacing indoor air with fresh air from outside.
- unclesaamm 6y ago
  The article links to the study. The issue was more than certain people sat downwind of others indoors, rather than where the air came from. Let me know if you read a different conclusion from it.
  - beamatronic 6y ago
    Now I’m really curious. How does one exchange indoor air safely?
- deleted 6y ago
  [deleted]
- felbane 6y ago
  As I understand it, the restaurant had an air conditioner in front of a table, and an infected but asymptomatic person was breathing into the airstream which was then circulated to infect anyone downwind of the a/c.
doliveira 6y ago
I was under the impression that the aerosol route was just common knowledge, but last week my state government (in Brazil) was doing deep cleaning in schools that have been closed for like 100 days. Yeah, good thing you're deep cleaning probably the last place on earth with no coronavirus! Now we'll only have problems if people want to breath in there... Such a stupid security theater.

ianpenney 6y ago

https://www3.nhk.or.jp/nhkworld/en/news/ataglance/855/ https://www3.nhk.or.jp/nhkworld/en/news/ataglance/855/ From April, Japan has been on top of this for a little while. Impressive science imho.

sukilot 6y ago
And yet Japanese government declared victory and campaigned against protective measures leading to a massive re-ourbreak, "for the economy"
- addHocker 6y ago
  Those who pay, get to set the agenda. And its hard to convince a CEO who thinks money can move heaven and earth, that his influence should be limited by biology and physics.
- thiagocesar 6y ago
  Japan has some really impressive universities and, as a rich country, is able to nurture all sorts of talent. The Japanese ruling party is a bunch of old people from a few traditional families mixed with some new faces. It’s very unfortunate how little these two worlds (talented people and politicians) collide.

KoftaBob 6y ago

This comes to mind every time I see a company/business emphasize how much priority they're putting on keeping people safe, and then only speaking about disinfecting every surface throughout the day. While it doesn't hurt to keep surfaces clean, we continue to see evidence that the majority of cases have come from airborne spread in an enclosed environment with poor ventilation. If there's any lasting change to building environments that comes out of this, I think it should be an overhaul of building ventilation codes to require/heavily incentivize systems that replace air rather than circulate it.

lostapathy 6y ago
Because wiping high-contact surfaces a few times a day is cheap, easy to do, and highly visible. And, hopefully, an easy extension of nightly cleaning that was already happening. Reworking your HVAC system to provide better circulation, filtration, and/or more fresh air is expensive, often an ongoing cost, and probably invisible to the end customer. I guess you could say it's well-intentioned virtue signaling.

tgb 6y ago

One problem is that no one seems to know that AC systems recirculate air. I literally can't get people to believe me when I tell them this. When buying a window unit recently, some models had the ability to incorporate fresh outside air but the cheaper ones didn't. My home is leaky enough that I worry more about keeping outside air out rather than in, though.

bluGill 6y ago
The ones that bring in outside air (that I have seen) just let a little outside air in. Most of the air is still recirculated, but there is a tiny hole that opens to let some air in.
sukilot 6y ago
Do people not use the recirc switch in their car?
- tgb 6y ago
  I think this actually makes it more understandable. If recirc is a special mode you have to activate in your car's AC, then it's reasonable to assume it's not the default mode for your house AC too. Since they never had a 'recirc' button to press at home, they'd assume it doesn't recirculate. Reasonable, but inaccurate.
stx 6y ago
Unless someone who has it is inside your home I don't think you need to worry about the air recirculating. I agree though its amazing that people don't understand how this works.

graeme 6y ago

If anyone is in an indoor environment and wants to gauge risk, a portable co2 meter can be had for about $100-$150. Cod2 is a good proxy for indoor pollutants/air exchange, and I’m assuming it is a good proxy for aerosols too. I use one of these, you can use a portable battery to power it. https://www.amazon.com/AutoPilot-APCEMDL-Desktop-Data-Storage/dp/B07JDJP4HH/ref=sr_1_15?dchild=1&keywords=Co2+meter+autopilot&qid=1596467296&sr=8-15 https://www.amazon.com/AutoPilot-APCEMDL-Desktop-Data-Storag...

klysm 6y ago
It seems to be an even better proxy for aerosol risk compared to general circulation because co2 is coming from lungs - I might make myself a wearable logger
ketamine__ 6y ago
We're constantly filling the rooms we occupy with aerosols from our mouths. How will this help?
- function_seven 6y ago
  Because we’re also constantly filling rooms with the CO2 that we exhale. The CO2 meter acts as a proxy for how much exhaled “stuff” is lingering about. So if your CO2 meter shows that the room is at ~400ppm [:’(], rather than 800 or 1000, then you can deduce that the room is well ventilated. I’m other words, whatever ventilation removed the excess CO2 most likely also removed the aerosols at the same time.
  - driverdan 6y ago
    Considering atmospheric CO2 levels are around 400ppm you're not going to keep it that low indoors unless it's full of open windows.
    - graeme 6y ago
      Yup. I have all of my windows open right now, it’s summer. Co2 tends to be around 500. Even outdoor city air in my location is more like 450, though of course my meter could be biased high.

R0b0t1 6y ago

This is a good article. I work at a biotech company that studies virus transmission and helps others study it. It was clear from the very beginning that transmission was airborne. Why would it not be? That the WHO and some doctors were assuming it was not seriously damages their credibility as healthcare professionals. Current events should lead people to seriously question deference given to doctors. They need to be held accountable for their actions and must be made to listen to professionals in other fields.

aantix 6y ago
Why wasn't there a large spike with the recent protests in the participating demographic? https://www.forbes.com/sites/tommybeer/2020/07/01/research-determines-protests-did-not-cause-spike-in-coronavirus-cases/ https://www.forbes.com/sites/tommybeer/2020/07/01/research-d... The chants "no justice, no peace"? "I can't breath"? Those were clear chants. Everyone breathing on each other while chanting. Unencumbered by a mask.
- squeaky-clean 6y ago
  > Unencumbered by a mask. Got a source on this? From the protests I've been attending, I'd say mask usage is easily at 99% of attendees. Everyone pictured in your linked article also has a mask, at least 10% have full masks and face shields.
  - derg 6y ago
    hell at the ones I went to there were roving groups of people handing out masks and gloves (more masks than gloves and the masks came directly from the box), hand sanitizer, and water. it was a sight to see honestly and very heartening bit of community and mutual aid.
- machello13 6y ago
  That's only a single paper, hardly conclusive. But also: > Unencumbered by a mask. The picture at the beginning of the article you linked shows every protester wearing a mask.

kenjackson 6y ago

There is a weird disconnect. Everyone seems to acknowledge the most likely way to transmit COVID is via droplets when indoor. Yet, there is little discussion about ventilation. Maybe people felt like there was less they could do?

KoftaBob 6y ago
If I had to guess, it's because sanitizing surfaces all day is cheaper/easier than upgrading the ventilation system.
obelos 6y ago
I think this is it. Everyone's painting the roses red because spritzing some sanitizer on every surface costs a minuscule fraction of the massive revamping of indoor climate that's actually required to reduce risk.
ghaff 6y ago
>Maybe people felt like there was less they could do? Probably mostly that plus a lot of the attention focused on transmission by touch early on. The last event I went to in March there was no handshaking, cleaning of surfaces, etc. But no masks or distancing. But, yeah, taking additional care to clean surfaces is pretty easy and cheap. Completely redoing ventilation is going to be pretty much impossible in a lot of situations.
ehnto 6y ago
Gyms and restaurants have had their air conditioning off in Aus. Israel turned off their bus air conditioning. This isn't breaking news but I suspect it would be a new angle to the media rhetoric for a few countries and media outlets.
- Bootwizard 6y ago
  It's the middle of summer in the US so that's not going to go over well here. Just another thing for Karens to yell about and get on the news.

jennyyang 6y ago

After this pandemic, doctors and scientists are going to have to come up with more media-friendly terms from now on. The problem is that "airborne droplets" and "airborne" sound too similar and it's very hard for regular people to understand what that means. "Airborne droplets" means that viruses need saliva to transmit between people. "Airborne" means that the virus only needs dust particles to transmit to other people. Measles is airborne transmission, which means that if someone with measles enters a room, that room can be infectious for 12+ hours because viruses will be infectious in the dust. If someone with coronavirus sneezes in a room, the large heavy droplets will quickly fall to the ground. If you breathe in the droplets then you can catch the virus, but these only stay in the air for seconds. However, there are microdroplets which stay in the air for 30+ minutes depending on the air currents. So there is a distinction between them. If coronavirus were truly airborne, then we would all need to wear masks all the time, even when no one is around. No where would be safe and we would have to implement extremely strict lockdowns. But the fact that scientists and doctors have chosen to use the term "airborne" in both have made it extremely confusing and given how quickly information and misinformation is disseminated these days, they need to choose terms with care from now on.

enraged_camel 6y ago
The article addresses this midway through. The problem is that even the experts haven't really agreed on terminology. They need to do that first before they can hope to inform the public. :)
- mc32 6y ago
  So why talk about HVAC systems ? Context: >” by 10 bottles of hand sanitizer without a word on ventilation—whether it was opening windows, employing upgraded filters in its HVAC systems, or using portable HEPA filters. It seems baffling that despite mounting evidence of its importance, we are stuck practicing hygiene theater...”
  - enraged_camel 6y ago
    Sorry, what do you mean?

deleted 6y ago

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misanthropian00 6y ago

Yes it's a well written article by a clearly intelligent author who did his homework and knows his sources and of course we should never have ruled out short range aerosols. It's ridiculous. I think it only happened because so many people just believe whatever authorities like the CDC and WHO tell them without any critical reasoning applied. If these health agencies had not effectively ruled out the possibility afaik without any supporting evidence maybe there would have been more research to figure out droplet sizes and travel paths under various airflow conditions. Currently everyone seems to just want to make assumptions and stick to them, but that isn't science even if you call yourself a scientist. Maybe also N95 masks would have been considered essential not only just to health care workers and maybe more effort might have been made to supply some to the general population. Currently 3M for instance voluntarily stopped selling their masks except to hospitals and speaking of those masks there is also not enough research on effective ways of decontaminating those masks without reducing their filtration effectiveness so that they can be reused more often and so that more can be made available to the public instead of effectively making them hospital only.

ColanR 6y ago

We probably aren't hearing about it because it's something we have less ability to protect against. I remember a popular comment here a while back mentioning that epidemeologists' job is partly public relations, trying to figure out what they can tell the general public that will minimize the viral spread. Making sure everyone wears masks will, at the scale of the general population, reduce the infection rate by some noticable percent. It's also something everyone can do, and it gives everyone a sense of control over the situation - enough of a sense, at least, to prevent chaos. Talking about airborne transmission, though? The kind of masks that can protect against that are hard to come by. Not to mention that the virus could enter via the fluid of the eyes (not trying to add conspiracy here, just trying to make a point about the difficult reality of preventing infection [0]). Bio-rated goggles and N95+ rated masks are more than we can expect from a public that's making face masks out of bandannas. I think we're seeing very pragmatic statements being made, that are tailored to a public that can't enter full biohazard mode and need to not panic. [0] https://www.biorxiv.org/content/10.1101/2020.05.09.085613v2 https://www.biorxiv.org/content/10.1101/2020.05.09.085613v2

sigstoat 6y ago
> Talking about airborne transmission, though? The kind of masks that can protect against that are hard to come by. Not to mention that the virus could enter via the fluid of the eyes (not trying to add conspiracy here, just trying to make a point about the difficult reality of preventing infection [0]). Bio-rated goggles and N95+ rated masks are more than we can expect from a public that's making face masks out of bandannas. plenty of evidence that even a little bit of protective gear helps. it isn't a matter of hazmat-suit-or-GTFO.
- ColanR 6y ago
  > Making sure everyone wears masks will, at the scale of the general population, reduce the infection rate by some noticable percent. I said that.
- ghaff 6y ago
  I think that's what the parent was saying. The widespread wearing of just about any face covering seems to help on net even if it's probably >50% about protecting other people. Even if higher-level protective gear were readily available, most people wouldn't wear for any length of time and it wouldn't be fitted properly. So just wear something seems to be the most reasonable advice for the general population.

sigstoat 6y ago

i wish target and home depot would stop making us wait in line while they futz about wiping things down. it's been clear that time spent in line with other people is a bigger concern than the possibility that something is lingering on the barcode scanner and will be transferred onto my box of nails, or bananas.

scythe 6y ago

One issue is that we seem to have an all-or-nothing view of infection. People think that either a virus gets in your nose and you get sick, or it doesn't and you're fine. This extends to thinking that either there is a risk or there isn't, which motivates incorrect anti-mask arguments. In reality, the probability of infection varies continuously with the degree of exposure, and the minimal infective dose might be prevented even if not all viral particles can be blocked. https://en.wikipedia.org/wiki/Minimal_infective_dose https://en.wikipedia.org/wiki/Minimal_infective_dose With airborne transmission, it is practically impossible to reduce the transmission probability to zero in many situations, and we have overlooked the value of finite improvements. However, the circumstantial evidence suggests that, since super-spreader events are correlated with apparently high airborne concentrations of viral particles, that reducing the duration and intensity of exposure may yield significant benefits even if inhaled air cannot be made completely free of virions.

deleted 6y ago
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acqq 6y ago
Exactly, that "all or nothing" is the main problem in in how most of the people think about the whole topic. I've read one work that gave the very simple estimates: if the infected person wears the surgical mask it will emit 50% less in the air, and if the non-infected person wears the surgical mask that person will get 60% of what's in the air. But combined, that means that the non-infected person will get around only 30% of what it would get when nobody would wear a mask. Which seems to be way too little for personal "full" protection, but looking more globally: If the R factor (reproduction number) is 2.7 with no measures, and if everybody wears a mask and other limitations are respected (physical distancing, limiting the number or people in the closed spaces, ventilation, etc.), all together it can result in the R factor being reduced to less than 1: With the known no-measures factor 2.7 we have exponential growth. With the factor under 1, we have a steady decay in the number of infected people. There we also "just" have to reduce that factor to 30% of the no-measures one. It's not so easy as some people spread to many, and a lot already don't pass the virus to others. That's why groups of people near each other change everything too much. But just by maintaining the factor under 1 (the lower the better) we guarantee that the relative number of infected around us will be always be smaller and smaller, and that's can be more than enough for the population as the whole. That's why wearing the masks and any additional good measures together do help, even if every measure, evaluated alone, for only one person, "doesn't protect" enough. So it is not just either 0 or 100%, but everything in between: not everybody has to use the same protection that the medical workers have to to improve the chances for everybody. But everybody should do it. One person who's actually infected and not wearing its mask changes the number of viruses passed to anybody in its vicinity from 30% to 60%, when all the rest wear the masks, or to 0 to somebody who's also not wearing the mask. From the starting 50% and 60% of masks "working" we get all the other outcomes too. And the same is valid for testing. Rapid wide scale cheap testing to identify who should enter the building doesn't have to be as good as PCR tests to still give us immense benefits, if we have it and use it. We just have to be clear that we want it, and that we know now it's not about "either 0 or 100%." Also, the pictures (and the video) explaining much more than many words: "Face coverings and mask to minimise droplet dispersion and aerosolisation: a video case study" https://thorax.bmj.com/content/early/2020/07/24/thoraxjnl-2020-215748 https://thorax.bmj.com/content/early/2020/07/24/thoraxjnl-20...

MiguelVieira 6y ago

When I look at this heat map of recent cases per capita in the US https://globalepidemics.org/key-metrics-for-covid-suppression/ https://globalepidemics.org/key-metrics-for-covid-suppressio... the first thing I see is hot spots all across the southeast and desert southwest. These places have widely varying governments and cultures, but the one thing they do have in common right now is: they're hot. My suspicion is that many of the outbreaks we've seen recently are caused by people from different households congregating indoors in buildings with air conditioning and closed windows. The article mentions this, but I rarely here it talked about on the news: "The importance of aerosols may even help explain why the disease is now exploding in the southern United States, where people often go into air-conditioned spaces to avoid the sweltering heat."

sp332 6y ago
And this might switch in winter, as people in the south get outside more and the north buttons up for the cold.
milesvp 6y ago
This is something I currently speculate too. Hotter states really benefited from AC allowing people to live there comfortably. I think it might show us what’s coming as people move indoors in colder months elsewhere. It’s getting harder and harder to stay away from people from a purely psychological standpoint, and I think fall is going to get bad in the PNW as people congregate indoors to stay out of the wet and cold.
Vysero 6y ago
Ben Shapiro has been saying that for months..

js2 6y ago

A couple other articles I've read in the last few days also cover this topic: Yes, the Coronavirus Is in the Air > Transmission through aerosols matters — and probably a lot more than we’ve been able to prove yet. ... > I am a civil and environmental engineer who studies how viruses and bacteria spread through the air — as well as one of the 239 scientists who signed an open letter in late June pressing the W.H.O. to consider the risk of airborne transmission more seriously. https://www.nytimes.com/2020/07/30/opinion/coronavirus-aerosols.html https://www.nytimes.com/2020/07/30/opinion/coronavirus-aeros... Aboard the Diamond Princess, a Case Study in Aerosol Transmission > A computer model of the cruise-ship outbreak found that the virus spread most readily in microscopic droplets light enough to linger in the air. https://www.nytimes.com/2020/07/30/health/diamond-princess-coronavirus-aerosol.html https://www.nytimes.com/2020/07/30/health/diamond-princess-c... And here's an article from two weeks ago that goes into some depth on superspreading events: https://www.washingtonpost.com/health/2020/07/18/coronavirus-superspreading-events-drive-pandemic/ https://www.washingtonpost.com/health/2020/07/18/coronavirus... > He believes ventilation may also be to blame for a case involving a young man from China’s Hunan province, who sat in the back of a bus but ended up infecting seven others in various areas of the vehicle and then two more on a second minibus he hopped onto next. Li interviewed the patient, driver, passengers and reviewed video footage and found it odd that few of those who became infected were nearby. In fact, at least one passenger who fell ill was as far away as possible at the front of the bus — 31 feet away — from the coronavirus-positive man. […] In the case of the Hunan man who transmitted the virus while riding two buses, Li said that “amazingly” after that four-hour window of infectivity, he is not known to have infected anyone else at all.

nabla9 6y ago

Just look at the list of people who signed the letter. They are experts in their field but they don't have the expertise to consider the whole picture. It's possible, that there is some airborne transmission besides droplets, but there is no evidence that it's significant transmission route. To get infected you need big enough dose of virus at once. Just some dry floating particles in the air is not enough.

thinkingemote 6y ago

in the UK the LNER train company highlights ventilation amongst other things, but the ventilation bit I found suprising when I encountered it. https://www.lner.co.uk/travel-information/lets-travel-together-safely/ https://www.lner.co.uk/travel-information/lets-travel-togeth... " Our onboard ventilation systems are providing a continuing supply of fresh air which is cycled every 6 minutes limiting droplet transmission between passengers." With the graphics implying that ventilation is spatially limited.

tialaramex 6y ago
The closest to air-conditioning possible in trains like LNER's is more similar to individual window units (except mounted in the ceiling) than the integrated systems in larger homes or offices. LNER operates two types of multiple-unit from the same family (a conventional EMU and then a bi-modal hack of that concept because the Tories don't want to spend money electrifying more of the railway), and then an older loco-hauled passenger service where a type 91 is pulling and there's a train of mostly passive passenger stock behind it. In both these designs there is electricity available, to run the air conditioning units, but it's not practical to pump air around the train so they don't. The air in your part of the train will get recirculated by the fans that make the air conditioning unit work, so I'd expect that if you spent an hour on a train four seats from an infectious person there's a decent chance you'll be infected. But air from other carriages isn't recirculated into yours at more than negligible level. Because these are mostly doing intercity journeys (thus fewer stops, and perhaps dwelling for longer at each) even the newer EMUs were not designed as a single huge tube like the modern Tube stuck or some local EMUs. So there's a "double airlock" partition between one carriage and the next which reduces noise and discomfort but makes getting on and off take a little longer. In this particular case it probably makes the train slightly safer to use.

eqdw 6y ago

Talking about airborne transmission would make it too obvious that masks are pointless security theatre. Can't have that

DoofusOfDeath 6y ago

The article makes an excellent argument for the plausibility of indoor airflows being a major transmission vector. But I didn't see anything about ongoing research to quantify the transmission risks posed by aerosols vs. other transmission mechanisms. (Maybe I missed it?) It's hard to make policy recommendations regarding aerosols if (a) we're not really sure how big a risk factor they pose and (b) the mitigations would be very expensive.

whydoyoucare 6y ago

I think we can't talk about it because there is no agreement on terms, modes of transmission, etc. and public policy cannot be based on ambiguous terms (though it can be based on imperfect data).

lurkmurk 6y ago

The amount of unknown and disagreement after all this time and money spent is a big failure of science. Laymen have a unique peak into how science works day to day, which might be good or bad depending on how you see it.

mensetmanusman 6y ago

I am still shocked: months after research has shown that SARS-CoV-2 is airborne stable in aerosol form for over 3 hours, we still aren’t telling the public that room air purifiers are a ‘good thing’ (for making indoor air like outdoor air - in regards to virion density per cubic air volume) The filter technology is essentially the same as in the N95, orders of magnitude more effective than cloth masks. Put these indoors, multiple per classroom/working space to help the air refresh in sub 5 minute intervals.

ogre_codes 6y ago
My wife works in a doctors office which has stayed open through the pandemic. She sees a few people a day in a small room. The very first thing she did after the pandemic hit the US, was buy an air purifier and she runs it continually. I'm quite surprised that they aren't more common in medical offices in general. The benefits of the air filter are cumulative with other protections—particles caught by the filter can't bypass the mask. Filters should be mandatory in any enclosed room, the fact that they don't even talk about them as part of the discussion about schools and businesses opening is mind boggling to me.
- yellow_postit 6y ago
  Expect we will see a repeat of the bungled rush for air purifiers as we did with ventilators.
  - ogre_codes 6y ago
    As with the ventilators, a bungled rush for them is better than not using them at all. Obviously if they had a more ordered distribution it would be better, but any movement in the correct direction would be an improvement.
  - mensetmanusman 6y ago
    Here would could at least prioritize schools? Ventilators was only bungled because it turned out to be the wrong therapy... air purifiers is a win win win

cblconfederate 6y ago

At the beginning of the epidemic, joe rogan hosted M.Osterholm for an interview where he warned about a lot of the things to come: the rapid spread, the small effect of washing hands or masks, the airborne spread etc. It's sad that the epidemic seems to have turned worse than most ppl assume it would.

mensetmanusman 6y ago

I am sympathetic to what the WHO did here, they realize that the average person is going to be extremely fearful when they realize that stagnant air could contain virion particles hours after being sneezed in (which is what the data show). They should have erred on telling people, because then we would have had months to ramp up room air purifiers before school starts... (I have been saying this for months, and am surprised by the lack of scientific leadership in ‘science’ organizations).

klysm 6y ago
Why should the WHO not incite fear if the fear is entirely rational and justified? People not being afraid enough is exactly how people die.

prof-dr-ir 6y ago

I would like to make a small point about the letter signed by "hundreds of scientists around the world". According to the NY Times there were in fact 239 signatories, which coincidentally is almost the same number as the "253 ... scientists from 44 nations" warning of the dangers of electromagnetic radiation (!) that can be found at https://emfscientist.org/ https://emfscientist.org/ . If you trust one, do you trust the other also? Regardless of the merits of the rest of the article, I would caution against trusting a claim just because two hundred odd scientists from all sorts of disciplines were willing to sign an open letter. Science is not a democracy.

briandear 6y ago
The “appeal to authority” is also used to sell toothbrushes. I agree that it’s foolish to trust an article or “fact” because 9 out of 10 doctors agree. I am very interested in why that 10th doctor didn’t agree..

CogentHedgehog 6y ago

There's one key paragraph buried in the article that will help a lot of people: > However, to date, there is also no evidence of truly long-range transmission of COVID-19, or any pattern of spread like that of measles. Screaming “it’s airborne!” can give the wrong impression to an already weary and panicked public, and that’s one reason that some public-health specialists have been understandably wary of the term, sometimes even if they agreed aerosol transmission was possible. Cowling told me that it’s better to call these “short-range aerosols,” as that communicates the nature of the threat more accurately: Most of these particles are concentrated around the infected person, but, under the right circumstances, they can accumulate and get around. Translation: people can get infected further away than with larger droplets -- especially in stuffy, enclosed environments -- but distance still reduces the risks.

DoingIsLearning 6y ago
> people can get infected further away than with larger droplets Minor nitpick, you can think of aerosol transmission as plume of virus particles. Technically you can get infected long after the carrier has left a closed room, at which point the concept of being "further away" stops applying.
- CogentHedgehog 6y ago
  That's true, in this case "further away" is a 4-dimensional distance vector (it includes time). :D

jsonbourne 6y ago

There is this startup which came up with the solution for the airborne problem. https://yourstory.com/2020/07/startup-bharat-kanpur-crestkiting-retail-air-purification https://yourstory.com/2020/07/startup-bharat-kanpur-crestkit...

rurban 6y ago

There are no receptors in the mouth, only nose and eyes. So the mouth does not need to be protected passively, the only problem is that the mouth is the only actor to spread the virus effectively.