16 ms·
Modeling the effectiveness of respiratory masks in reducing influenza (2018)
- tristanj 7y agoMore here: Study finds N95 masks reduce risk of coronavirus infection https://www.livescience.com/respirators-prevent-coronavirus-infection-study.html https://www.livescience.com/respirators-prevent-coronavirus-... As Wang's study revealed, rates of infection differed between doctors and nurses with [N95] respirators and those without. Specifically, the authors examined data collected from Jan. 2-22 at six departments within the Zhongnan Hospital. Within the 10-day period, the hospital treated 28 individuals with confirmed cases of COVID-19 and 58 "suspicious" cases. The medical staff in each department followed different safety protocols when treating the patients. About 280 medical staff in the hospital's Respiratory, ICU and Infectious Diseases departments wore N95 respirators and washed their hands frequently, while about 215 in the departments of Hepatobiliary Pancreatic Surgery, Trauma and Microsurgery, and Urology wore no masks and disinfected their hands less frequently. Although the respirator group encountered confirmed cases more often than the unmasked group — more than 730% more often — no one in the respirator group became infected. In comparison, 10 people in the unmasked group contracted the novel disease, despite treating fewer infected patients. "It would appear that N95 respirators, no surprise, protect against health care acquisition of the virus," said Dr. William Schaffner, an infectious-diseases specialist at Vanderbilt University in Tennessee, who was not involved in the current study. The small study is "reassuring in that sense," although there was no reason to think that N95 respirators wouldn't block out the novel coronavirus effectively, he added.
- chrisco255 7y agoI wonder how this squares with the fact that 2 healthcare workers in California treating a coronavirus patient contracted the disease? I presume they were wearing masks. See: https://mobile.twitter.com/skarlamangla/status/1234260334363308033/photo/1 https://mobile.twitter.com/skarlamangla/status/1234260334363...
- deleted 7y ago[deleted]
- onetimemanytime 7y agoOne mistake and you got it. Take out mask, touch clothes and then nose or whatever. Procedures are great for the first minute or two...after that unless you're super-trained and do that day in and day out, you'll make mistakes.
- testplzignore 7y agoThey probably were not wearing a mask. It's possible the patient never encountered anyone wearing a mask until the moment that coronavirus was considered as a diagnosis. My basic understanding of this is that it is simply uncomfortable for healthcare workers to wear masks all of the time, and they interfere with patients being able to see their faces (which humans usually like, even when it is a bad idea). I am interested to hear from anyone in the healthcare field regarding this and if there are any policy changes being put in place, even in regions where coronavirus hasn't (knowingly) spread to yet. From a layman's perspective, it would make sense to require every healthcare worker - particularly in ERs - to immediately start wearing masks.
- asdff 7y agoThere aren't enough masks in the U.S. to equip every healthcare worker for the duration of this virus.
- mikekchar 7y agoHaving spent considerable time at the hospital in Japan in the last few years, it now seems strange to me. Even my GP, In the 7 years or so that I've been seeing him, I've only ever seen him without a mask once (and I unfortunately get to see him a good 20 times a year :-P). Cultural differences are so strange...
- asdff 7y agoI'm referring to an n95 mask, but I'm betting in Japan workers are just wearing surgical masks. There are plenty of surgical masks in the U.S., of course. They aren't for this purpose, though. I'd assume it's for cultural reasons that surgical masks are worn that much in Japan, probably just makes patients feel comfortable. Surgical masks are to protect frail patients from your spit and snot, or to keep your spit and snot out of an open body during surgery. Wearing one won't protect you from disease.
- yodon 7y agoThat sounds like a study of N95 masks vs no masks, not N95 masks vs surgical masks. Another study reported here on HN compared N95 masks against surgical masks for respiratory viruses and found no significant difference between N95 and surgical masks[0]. [0] https://news.ycombinator.com/item?id=22456037 https://news.ycombinator.com/item?id=22456037
- vonmoltke 7y agoThat's not really what the study found. It found "there were insufficient data to determine definitively whether N95 respirators are superior to surgical masks". That is not the same as "found no significant difference between N95 and surgical masks".
- ghostpepper 7y agoHow can they discount the fact that handwashing protocols also differed?
- tgb 7y agoSo the mask group was also competely confounded with being infectious disease specialists? Perhaps there were other precautions besides masks and hand washing that they were taking due to their training, even if not explicitly. Still interesting, particularly given the widespread appearance of "don't bother with masks" articles these days.
- TylerE 7y agoNo. Piling up multiple layers of a completely ineffective barrer does not make it effective.' It'd be like trying to use layers of netting to hold back the sea.
- npsomaratna 7y agoYes - that is what I noticed as well. The two populations have different levels of expertise re: dealing with airborne infectious diseases; different frequencies of hand-washing; and no masks vs. masks. There are just too many confounding factors here to draw a conclusion (in isolation) re: mask effectiveness. Edit: in addition, the departments used to dealing with airborne infectious disease may have had specialized protocols and policies that the other departments did not have.
- boulos 7y agoI do think that on a personal level, it was probably just more hand washing, the masks to prevent droplets and so on (that is, both groups could have done so, but the infectious disease experts are more likely to do so with every interaction). However, one part of your comment stood out to me: the infectious disease units also have higher HVAC standards than say regular areas (e.g., https://www.hfmmagazine.com/articles/3246-studying-airflow-in-the-or https://www.hfmmagazine.com/articles/3246-studying-airflow-i...).
- amarshall 7y agoMost of the “don’t bother with masks” is usually about cheaper masks which are not rated N95.
- jvanderbot 7y ago
- coconut_crab 7y agoBut N95 masks aren't cheap and AFAIK must be disposed after one day of usage. So they must be reserved for the medical workers, while the other can use 3 or 4 layers surgical masks, which should provide adequate protection.
- TylerE 7y agoThey are pretty cheap in bulk when not in the middle of a supply crisis. Like a dollar or so each.
- coconut_crab 7y agoStill 25 times more expensive than 3 layers surgical masks, which costs like two dollars for 50 pieces. Oh yeah and I don't live in the US so my definition of 'expensive' can be different.
- TylerE 7y agoThink about how many disposable gloves the average healthcare worker goes through. Dozens per shift, at least. Those are about 5 cents a pop, easily more than a dollar per day.
- rvnx 7y agoAfter 3 hours only :|
- gyrgtyn 7y agoThis seems very simple and cost effective?
- gcb0 7y ago> compliance in donning the device after a look at the FDA page on the correct process (don't have access to the original article's references, so i will assume they used the FDA document): you are dead in the upcoming flu outbreak if you 1. use glasses, 2. sport a beard, or 3. happen to be a kid.
- Leary 7y agoThe US has 12 million N95 in stockpile, another 5 million N95 that expired. The US has 30 million surgical masks in stockpile. The US needs 300 million N95 masks for medical professionals. [1] [1] https://www.cnbc.com/2020/02/28/us-mulls-using-sweeping-powers-to-ramp-up-production-of-coronavirus-protective-gear.html https://www.cnbc.com/2020/02/28/us-mulls-using-sweeping-powe... Therefore it is rational for public health policy to reserve high quality masks for medical professionals, regardless of their effectiveness for the general public. I wonder how many masks they can manufacture a week in this emergency.
- pkaye 7y agoThe only US mask manufacturer says his current maximum is 600k masks/day. https://www.washingtonpost.com/business/2020/02/15/coronavirus-mask-shortage-texas-manufacturing/ https://www.washingtonpost.com/business/2020/02/15/coronavir...
- boulos 7y agoThey are not the only manufacturer. From the article: > Prestige Ameritech, the largest full-line domestic surgical mask manufacturer, was producing 600,000 masks each day but struggling to meet demand. Even if it’s true that they’re the single-largest manufacturer, they’re definitely not the only one.
- qiqitori 7y agoJapan's producing 100 million per day according to a couple articles I've read, e.g.: https://www.asahi.com/articles/ASN2W7QGVN2WULFA023.html https://www.asahi.com/articles/ASN2W7QGVN2WULFA023.html Another article suggests that this is three times as much as usual: https://www.yomiuri.co.jp/economy/20200228-OYT1T50288/ https://www.yomiuri.co.jp/economy/20200228-OYT1T50288/ Still not enough. :/
- vonmoltke 7y agoIn addition to what boulos said, this company makes surgical masks. N95 respirator masks are manufactured in the millions annually by 3M because they are used heavily in the trades. That said, I don't know where 3M manufactures them, so that supply could be disrupted.
- dieselerator 7y agoI wonder how it feels to be assigned to the control group?
- deleted 7y ago[deleted]
- droithomme 7y agoThanks for this. The US Surgeon General needs to be fired and delicensed from medical practice after his claim yesterday that no one should buy masks because masks don't work. He has no business representing himself as a qualified medical professional. His statements are such egregious malpractice that they rise to the caliber of extreme negligence and should expose him given his position to liability and possibly criminal charges for contributory homicide. South Korea is looking at charging church officials with "murder through willful negligence" (https://www.nytimes.com/2020/03/01/world/coronavirus-news.html https://www.nytimes.com/2020/03/01/world/coronavirus-news.ht...). The reason? They told church members to remove their masks during services as it was "disrespectful to God." Telling people not to wear masks is murder through willful negligence.
- asdff 7y agoMasks don't protect you from others, they protect others from you, and if you are a health professional dealing with infected people from vulnerable populations, or a surgeon asking for a scalpel over an open body, you are going to assume that you are infected and capable of transmitting disease out of an abundance of caution. Masks for the general healthy public is borderline hysteria and affects the medical supply chain.
- nec4b 7y agoRespiratory masks do indeed protect you from others. This is the whole point of this article.
- asdff 7y agoI wasn't saying n95 respirators don't do anything. They are very effective. I was talking about disposable surgical masks that people are now wearing everywhere.
- droithomme 7y agoYou should consider reading the scientific study that this entire thread is about. > In this article, a risk assessment model previously developed in general form was used to estimate the effectiveness of different types of protective equipment in reducing the rate of infection in an influenza outbreak. It was found that a 50% compliance in donning the device resulted in a significant (at least 50% prevalence and 20% cumulative incidence) reduction in risk for fitted and unfitted N95 respirators, high-filtration surgical masks, and both low-filtration and high-filtration pediatric masks. An 80% compliance rate essentially eliminated the influenza outbreak. It's not the only study. https://www.sciencedaily.com/releases/2019/09/190903134732.htm https://www.sciencedaily.com/releases/2019/09/190903134732.h... > Summary: The study reported 'no significant difference in the effectiveness' of medical masks vs. N95 respirators for prevention of influenza or other viral respiratory illness.
- bouncycastle 7y agoI did my own little experiment with masks which you can also easily repeat the experiment yourself. Note that this works on the regular masks you can buy from regular shops such as convenience stores that the general public mostly wears. Put on the mask in cold weather or a chill room and then take a deep breath and breathe out. You will notice a lot of steam is coming off around the sides of the masks and especially around the nose area where these masks are not sealed. Worse if you cough of sneeze! This is even more so after the mask has been worn for some time and gets soggy. Next, go outside and ask your friend to light a cigarette and exhale smoke in your face while you take a deep breath through your nose. (Wearing the mask as you would normally do). You will find a lot of smoke gets around the mask, mostly around the edges around the nose. You can make your own conclusions from there. My conclusion was that these things are mostly toys and the majority of people wearing them either do not fit them correctly or do not change often or both, and they also may be putting too much confidence in them.
- scarejunba 7y agoMask fit is important and that's why fit tests evaluation is done for medical professionals so what you're saying has basis. I wonder if the decreased number of pathogens makes it a different story, though. For instance if you cut down encountered viral load by 95% do you still have equal likelihood of illness?
- saurik 7y agoAs I imagine you are expecting to test for smoke in that case by seeing if you can smell it: of course you can smell it, as what you are smelling there is a gas. An N95 mask filters particles larger than some reasonably large size, which hopefully includes giant encapsulated viruses filled with genetic material but is not going to include the odor from smoke which is made up of individual molecules of stuff like syringol. An N95 mask is not some kind of "only oxygen and nitrogen and carbon dioxide (and whatever else you absolutely need from air)" filter: it is just that most scents thankfully aren't harmful, but happen to be correlated with stuff that is. FWIW, when I wear an N95 mask I do not get steam from its edges (that is either a ludicrously poor fit or you are expecting to be able to breath out too quickly for your mask design), but you also need to remember that breathing out is "safe" while breathing in is not, and yet the pressure in the two cases is very different, so something can be very effective even if it has the issue you are complaining about (and some masks are even designed specifically like that, with pressure vents to make breathing easier so you can exhale quickly without a problem and then pull air in more slowly where the feedback is more clear).
- KKKKkkkk1 7y agoAccording to Google Scholar, this paper has zero citations. This does not engender too much trust in its results.
- blackrock 7y agoFor something like this, I wonder why the health workers haven’t started using those positive-pressure helmet hazmat suits. Like those from that Outbreak movie.
- ruxmtl 7y agoAnyone have any info on the comparability of COVID-19 to H1N1 in terms of transmission methods since we have official trace data, studies and reports on H1N1? Am having this discussion and being pointed out the fact that H1N1's particulate size is actually smaller than COVID-19 (80-120nm vs 200nm respectively).