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Covid-19 Superspreader Events in 28 Countries: Critical Patterns and Lessons
- excerionsforte 7y ago"Three of the SSEs—in Japan, Skagit County, WA, and Singapore—involved concert-goers and singing groups belting out tunes together over a period of hours. (The Skagit example is particularly interesting, because the organizers were aware of the COVID-19 risk beforehand, and took the precaution of spacing out the participants by several feet. If they had been merely chatting, instead of singing, no one might have gotten sick.)" Imagine how bad Austin would have been if SXSW had actually gone ahead given how hellbent they were on going through with it. It would have been much much worse state than it is now. It is a positive that the government listened to health officials and shut it all down despite the complaining to the contrary. Economies never work well in sickened environments.
- uxhack 7y agoBut the article goes on to say that "common human activity that aren’t represented among these listed SSEs: watching movies in a theater, being on a train or bus, attending theater, opera, or symphony" But what I found interesting about the article (and it is long read) is his hypotheses on mode of transmission. Which is the "direct ballistic delivery of a large-droplet Flüggian payload from face A to face B" and that means that interventions like the "expanded use of masks and social distancing is critical" And we should also speak softly, avoid “coughing, blowing and sneezing,” or exhibiting any kind of agitated respiratory state in public, and angle their mouths downward when speaking." But he does warn that he is a Computer Scientist rather than having any medical background.
- klmadfejno 7y agoJust hypothesizing as well, but I think he might have it backwards. I'm not convinced you'll get magnitudes more virus in the ambient air from singing. But as a receiver if you're mouth breathing and taking deep breaths you're extra vulnerable. Nose hair is pretty effective
- agarden 7y agoIf the conductor wants you to make the consonants clear, then there will be spittle. Agreed that the deep breathing is likely just as important.
- f38zf5vdt 7y agoThe author seems to ignore the obvious confounding factor here of selection bias -- super spreader events all seem to deal with people who are in the same social circles rather than outside them, as would be the case in public transportation, movie theaters, gyms, etc. The reason being that events with people in social socials are readily traceable to an infected individual attending, whereas contact tracing for anonymous infection in a shared area is much more difficult. Even diseases with low transmissibility are known to be disseminated by public transit, such as tuberculosis. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4338233/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4338233/
- hammock 7y agoInteresting theory, why do you suppose a concert has more friends and less strangers at it than an opera or symphony?
- joshuahedlund 7y agoWell, I'd say there's a big difference between sitting silently in chairs at an opera or symphony and standing/moshing/yelling loudly in extremely crowded quarters at a rock concert.
- DataWorker 7y agoA lot of coughing and high risk individuals at the symphony though, unfortunately.
- daotoad 7y agoHigh risk for mortality, yes. But are they higher risk for actually catching the bug when exposed? I don't think anyone knows that. I'm not even sure how you could come up with numbers on how much viral exposure is needed to infect someone, short of controlled experiments with volunteers. The odds of killing a few volunteers seems pretty damn high, especially if you are testing with more vulnerable folks to establish a differential estimate. That's not a study I'd want to be involved in on either side of the clipboard.
- slg 7y ago>or exhibiting any kind of agitated respiratory state in public The only sizable population of people that I still see out in public that aren't wearing masks are joggers. I wonder if and when we will put a stop to that.
- malandrew 7y agoThis would also explain why many people are asymptomatic. They are still getting exposed but with a much lower viral load. Maybe the best "vaccine" here is just the lowest possible microdose of the coronavirus. We really should be looking at all the asymptomatic or low symptoms folks and figuring out what they have in common with one another. I would bet you it's just very low exposure, which gives the body more time to develop antibodies and mount a defense instead of the immune system being overwhelmed before it can adequately develop antibodies.
- gowld 7y ago> If they had been merely chatting, instead of singing, no one might have gotten sick. Really??
- ceejayoz 7y agoIt's entirely possible. Heavier breathing expels more droplets, and further.
- compiler-guy 7y agoIt also requires deeper inhalation by the receiver.
- SpicyLemonZest 7y agoIs it possible to test various mechanisms of infection on monkeys? Sprays at various concentrations in their noses, in their mouths, on objects in their environment. Seems feasible and useful, but maybe there are concerns about how the results would generalize. For extra credit, spray in their mouth through a basic cloth mask.
- Symmetry 7y agoIt would be illegal to do this with monkeys but ferrets have the same ACE2 protein we do and would be good candidates for this sort of research.
- dboreham 7y agoHmm...I swear I've read a paper talking about monkeys infected, having mild symptoms and then recovering. Perhaps it was a SARS-1 paper.
- James_Henry 7y agoThey do infect monkeys: https://www.thesun.co.uk/news/11026173/lab-monkeys-infected-with-coronavirus-in-race-to-find-life-saving-vaccine-to-stop-the-deadly-outbreak/ https://www.thesun.co.uk/news/11026173/lab-monkeys-infected-...
- Symmetry 7y agoIt could also be from outside the US?
- microcolonel 7y agoAre any monkeys even susceptible to it?
- SpicyLemonZest 7y agoI remember reading some study about monkeys reliably developing antibodies to it.
- nl 7y agoThis is a pretty good piece. The work done in the restaurant paper is really good. It was a clever natural experiment but clearly was a lot of work to piece together.
- londons_explore 7y agoI would like to think that in a global pandemic costing hundreds of thousands of lives, trillions of dollars of economic costs, and significantly lowering the quality of life of future generations, this research would have been done months ago. How hard can it be to find 100 similar workplaces, and to 33 of each say "You guys must wear masks". "You guys must have all windows open all the time". "You guys must wear gloves all the time". Then wait 5 days, and see how infections spread. That activity might lead to the deaths, in the worst case, of a couple of workers. Yet the knowledge gained would save tens of thousands.
- ebg13 7y agoWe can accomplish many great things if we knowingly discard ethics for the sake of efficiency, yes.
- vikramkr 7y agoNot really in this case though. Ethically there's not much of a concern with that study since we don't know what works so we're not doing any harm by prescribing known bad methods. The ethical harm would come from a poor study design that won't tell us anything useful. Getting good data from a study like this is really difficult, and we can't really accomplish anything by discarding good data for the sake of efficiency
- londons_explore 7y agoI question if modern ethics are perhaps too focussed of the wellbeing of the individual, at the expense of the wellbeing of all of us... Or, to put it more bluntly, a modern ethics committee would have rejected the idea of installing sewers in cities to prevent disease because one builder of the sewer might have died in the process. Without that, industrialisation probably would never have happened, and we'd all be subsistence farmers today.
- JamesBarney 7y agoThis is especially true with studies. Because it was thought unethical to conduct studies around masks and infectious disease, the evidence was sparse, so the WHO and CDC didn't recommend wearing them. This has directly led to tens of thousands of deaths.
- gdubs 7y agoFor all my cynicism with politics, I was really impressed that the mayor of Austin stepped up and forced the cancelation of SXSW. That’s an enormous amount of money for the community, and it could not have been easy. Not a lot of “lessons in courage” these days, but I really think that was one.
- PeterStuer 7y ago"The community" receiving this money in each of these cases refers to a very small percentage of the overall population of the region.
- gdubs 7y agoI would bet that the majority of small businesses in Austin bank on the yearly spike in traffic, and that missing out on that is a very big deal.
- Retric 7y agoAustin has more than 10x more people every day than attend SWSX which lasts for less than 2 weeks. It’s even less significant as many people avoid the area during big events. Perhaps a 5% increase in sales for under 3% of the year so what 0.15% increase as a high estimate over the year.
- giggles_giggles 7y agoAccording to this[1], SXSW brings Austin about $350 million annually. According to Wikipedia, Austin's annual GDP is about $1.5B so 350/1500 = roughly 23% of the city's annual GDP. Anecdotally I know of many people who work year round to prepare for an event at SXSW and rely on it for their entire annual income. Cancelling SXSW is a big deal to this city. It hurts. It's not to be downplayed. [1] https://austin.culturemap.com/news/city-life/09-27-17-economic-impact-sxsw-348-million-super-bowl/ https://austin.culturemap.com/news/city-life/09-27-17-econom...
- gns24 7y agoI'd been wondering why crowded public transport where people are breathing right next to one another hasn't caused massive spreading. This explanation makes a lot of sense - only when we cough or have to speak loudly do we exhale a significant amount of droplets.
- zaroth 7y agoWhat makes you think that crowded public transport didn’t pay a role in NY’s prevalence being so high?
- standardUser 7y agoPublic transit certainly didn't cause NYC-like levels of transmission in Japan, though it has a similarly dense public transit system.
- zaroth 7y agoDon’t riders almost universally wear masks on public transit in Japan?
- drpgq 7y agoNot sure why you're getting downvoted. Mask wearing percentages on public transit is quite different in NYC compared to Tokyo.
- jfoster 7y agoNot sure about universally, but certainly more commonly. Also, speaking loudly on trains is frowned upon. Speaking on your phone whilst on trains is not allowed.
- esyir 7y agoThey don't. Common etiquette there is to wear a mask when sick (they also wear them for allergies and warmth), but the majority (pre-covid) do not.
- 7y ago
- obelos 7y agoYeah, but did they control for people with “Germanic foreheads”?
- tzs 7y agoWay down in the article, it describes some data that was not included in its analysis but nevertheless is quite interesting, where several people in a restaurant were infected by one other patron. This is something straight out of a TV crime show: > As the authors note, the restaurant in question was air-conditioned on the date in question. Using video footage, they were able to chart the position of every diner in the restaurant, and then map their subsequent infection status in relation to both the single infected individual known to be present at the time and the air conditioning system’s outgoing and intake streams. If the primary transmission mode of COVID-19 were by small, sub-Flüggian airborne particles, the presence of the forced air convection might have made the environment safer (especially since “smear samples from the air conditioner [itself] were all [COVID-19] nucleotide negative”). But the researchers instead found evidence for the opposite: “The key factor for infection was the direction of the airflow,” with downstream individuals being most at risk—a result consistent with the thesis that COVID-19 is transmitted primarily through the ballistic transmission of large respiratory droplets. I could easily imagine that having been a key insight in an episode of "Bones" or "Elementary". (If you are looking for something good to binge watch during COVID "stay at home", I recommend "Elementary", currently on Hulu and CBS All Access. It's a Sherlock Holmes set in modern times series. They did a really good job of taking many characters and plots from the original stories and adapting them in such a way that if you read the stories you will recognize them and perhaps even think you know what is going to happen--but they have changed just enough that the ending will still surprise you but also be eminently reasonable in hindsight. The stories that aren't obviously based on any particular original are equally good).
- AnimalMuppet 7y agoWait a minute. > But the researchers instead found evidence for the opposite: “The key factor for infection was the direction of the airflow,” with downstream individuals being most at risk—a result consistent with the thesis that COVID-19 is transmitted primarily through the ballistic transmission of large respiratory droplets. If the direction of airflow is the key factor, then the droplets have to be moving with the airflow, and therefore not ballistic. Am I missing something?
- 7y ago
- riccardobrasca 7y agohttps://threader.app/thread/1252581933835575297 https://threader.app/thread/1252581933835575297 This is a super interesting point of view.
- war1025 7y agoI read through most of that but will admit that I don't quite understand what he was trying to get at. Can you summarize?
- dboreham 7y agoI only read the beginning, but it seemed to be about transmission not being completely transitive.
- baq 7y agoit more or less says that people who get met a lot (...directed graph, remember) somewhat counter-intuitively increase the total percentage of people infected more than you'd expect even if they don't transmit the disease after they contract it more than an 'average' person (again, directed graph).
- war1025 7y agoI guess that doesn't seem counter-intuitive to me. That's the whole reason behind social distancing right? To reduce the likelihood that you will contract the virus from someone else. It's not so much about keeping from getting other people sick, it's about keeping yourself from getting sick. As someone with young kids and a more frequent exposure to norovirus and other stomach bugs than I'd like to admit, once that gets into the family, everyone gets it. The way to avoid it is to not go places where your kid is going to pick it up (public library usually), but in general you still go to those places because they are convenient for other reasons. I understand the focus on handwashing and sanitizing things, but that doesn't do anything for direct exposure. If the stomach bug is near you, you're getting it. I assume coronavirus is going to be much the same.
- klmadfejno 7y ago
- thedudeabides5 7y ago"It is theoretically possible that socioeconomically privileged individuals really do lack some immune-response mechanism that protects individuals who have been exposed to a wider array of infectious pathogens. (A recent report on COVID-19 surveillance testing at a Boston homeless shelter contained the stunning disclosure that 36 percent of 408 screened individuals tested positive for COVID-19. Yet the vast majority were asymptomatic, and even the few who were symptomatic did not diverge statistically from the 64 percent of tested individuals who were COVID-19-negative.)" Interesting. Having spent some time in SF, can attest that the homeless - on occasion - appear to have super human immune systems.
- AnotherGoodName 7y agoI wonder if it's the case that the filtering out of any risk factors has already been done on the homeless population. Homeless people with marginal health unfortunately don't live long. Those that have survived a long life as homeless are very likely to be the most robust humans alive.
- tolstoshev 7y agoSurvivor bias. You're not seeing the dead ones.
- zzzcpan 7y ago> If small-droplet airborne concentrations in unventilated spaces were a common vector for COVID-19 transmission (as with measles, for instance), one would expect whole office buildings to become mass-infection hot spots. There is some logical fallacy here. Large droplets don't exclude aerosol transmission, so you can attribute to it everything you attribute to large droplets too. There are also such superspreading events of whole building getting infected past lockdown, like the whole family dorm building getting infected where people share bathrooms and such.
- tomohawk 7y ago> It’s similarly notable that airplanes don’t seem to be common sites for known SSEs, notwithstanding the sardine-like manner in which airlines transport us and the ample opportunity that the industry’s bureaucracy offers for contact tracing. Yes, New Zealand has one cluster that’s based around an infected but asymptomatic flight attendant. But the many known infections he caused took place at a wedding reception, not in an airplane. This flight attendant was running what was, in effect, an unintended experiment, with the passengers on board his aircraft playing the role of control group. And the results offer a microcosm of the nature of SSEs as a whole.
- barbegal 7y agoI think one of the things people over-estimate is how much evidence is used in making public health decisions. The UKs advice is to wash hands but not to use a face mask. Hand washing is essentially free but the cost of producing reusable cotton face masks for every single person would likely be ~ £1 billion. If that is money wasted, it is still extremely small compared to the economic devastation which could cost the UK government ~ £100 billion [1] and the economy as a whole significantly more [1] https://obr.uk/coronavirus-reference-scenario/ https://obr.uk/coronavirus-reference-scenario/
- Leherenn 7y agoI think the reticence to promote masks is that there's not enough of them. It's getting better, but if a month ago they had said "everyone has to wear a mask" it would have been a panic as people can't get hold of them, plus it would have been harder to get some for essential workers. If there had been massive stockpiles available, the message would have likely been different.
- heracles 7y agoThe general evidence for washing hands as an effective counter-measure is very very strong. It is a complete no-brainer, while decisions regarding face masks are complex and have to take into account lots of variables.
- barbegal 7y agoCan you point to evidence to back up your claim that "The general evidence for washing hands as an effective counter-measure is very very strong." Meta-studies show that the effectiveness of hand washing alone is minimal https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4891197/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4891197/
- heracles 7y agoI think you misread me, I meant "general" as in general counter-measure, not COVID19-specific. Clearly I should have been more precise. In a situation where overload of healthcare is a primary concern, recommending counter-measures against general infections (where hand hygiene qualifies) is a no-brainer.
- clairity 7y agoi take this as a positive sign that the national conversation might be starting to finally move beyond fear and panic to reason and understanding. the primary mechanism of transmission (droplets into the nasopharangeal area) has been known since at least february (when it started to become regular news here in the US) and probably since at least december in china when it became a known infectious agent. the better we understand the situations and environments where transmission is materially increased, the faster we devise reasonable mitigations and get back to some semblance of normalcy. it's also important to debunk false mitigations that only serve to mollify the skittish (e.g., elaborate germophobic rituals) and thereby obstruct understanding and cause other harms. in fact, some of those mitigations can increase transmission risk simply by providing a false sense of relief (e.g., constant, but inevitably incorrect, mask usage).
- andybak 7y ago> the primary mechanism of transmission [...] has been known I thought the entire point of this post was that there were multiple competing theories and little agreement or certainty? Your use of the phrase "has been known" implies a broad consensus in public health circles. I've seen very little consensus on any feature of this pandemic.
- macintux 7y agoThe fog of war seems to be relenting, but as a casual observer it's been maddening to see so much conflicting information and the corresponding cherry-picking of information to assert that this is overblown.
- clairity 7y agono, the point of the article was that while there are competing theories of transmission, the centrality of the ballistic transmission mechanism has been known for a while (from prior coronavirus studies) and has been relatively undisputed as the primary transmission vector. to wit (from the article), > "When do COVID-19 SSEs happen? Based on the list I’ve assembled, the short answer is: Wherever and whenever people are up in each other’s faces, laughing, shouting, cheering, sobbing, singing, greeting, and praying. You don’t have to be a 19th-century German bacteriologist or MIT expert in mucosalivary ballistics to understand what this tells us about the most likely mode of transmission."
- ra120271 7y agoWhen thinking about whether 2m social distancing is enough when coughs and sneezes can travel viable infected virus much further, my understanding is that governments care about onward transition rates. If on average an infected person infects less than one other person it will eventually fade out. So the question is does the 2m separation push the averages towards that? I would think it does. Partly because the number of people within a blast radius of a cough or sneeze is much lower, and secondly the probability of infection drops with distance. Social pressure that then drives coughing and sneezing people home in a social distancing environment probably reinforces the effect of reducing transmission rates. Is it enough? That will have to be measured and analysed probably much later.