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The two hair stylists in Springfield, Mo., broke the cardinal rule of infection control: Despite having respiratory symptoms, one went to work and saw clients for eight days, when she learned she had tested positive for Covid-19. Her colleague also developed symptoms, three days after her co-worker, and also kept working until she tested positive, two days after the first stylist. Together, they saw 139 clients, with appointments for haircuts, shaves, and perms lasting 15 to 45 minutes.

Yet when the local health department identified and contacted the 139 clients, asking them to self-quarantine for 14 days and checking in daily about whether they had developed Covid-19 symptoms, not a single one (of the 104 who agreed to be interviewed) did. Of the 67 who consented to a swab test, every one tested negative. There was one other notable fact about the case: Both stylists and every client had worn a face covering.

The stark case, described on Tuesday in Morbidity and Mortality Weekly Report, adds to the near-universal scientific consensus that, more than any of single action short of everyone entering solitary confinement, face coverings can prevent the transmission of the coronavirus that causes Covid-19.


“Like herd immunity with vaccines, the more individuals wear cloth face coverings in public places where they may be close together, the more the entire community is protected,” Robert Redfield, director of the Centers for Disease Control and Prevention, and two colleagues wrote in an editorial in the Journal of the American Medical Association, also published on Tuesday. Because cloth face coverings can also allow states to more safely ease stay-at-home orders and business closings, Redfield told a JAMA Live webcast Tuesday, “If we could get everybody to wear a mask right now, I really think in the next four, six, eight weeks, we could bring this epidemic under control.”

The “if,” of course, has been the problem. Because masking or refusing to mask has become a political statement, only 62% of Americans said in April that they did so (the CDC recommended the practice on April 3); in May, 76% said they did, according to another MMWR study. The CDC advice followed weeks of mixed and contradictory messaging, and even after it was issued, President Trump and other national leaders fell well short of endorsing face coverings.


Although mask wearing does not differ by gender, it does vary by region of the country. In May, 87% of people surveyed in the Northeast said they wore masks when going out in public; it was 80% in the West, 74% in the Midwest, and 71% in the South, where cases are skyrocketing.

Face coverings almost certainly explain why the Springfield hair stylists did not transmit the virus to a single client. Of the 104 clients surveyed, 102 said they wore a face covering (usually cloth coverings or surgical masks) during their entire appointment; two said they did for part of it. Both stylists were always masked.

The benefits of masking in reducing viral transmission are clear from much more than the unusual case of a Springfield hair salon, of course. In an unpublished analysis of 194 countries, those that did not recommend face masks saw per-capita Covid-19 mortality increase 54% every week after the first case appeared; in countries with masking policies, the weekly increase was only 8%.

And at the largest health care system in Massachusetts, Mass General Brigham, before administrators adopted a policy of universal masking for health care workers in late March, new Covid-19 infections in that population were increasing exponentially, from 0% to 21%, or 1.16% per day, on average, researchers reported in another JAMA paper published Tuesday. With everyone masked, the rate of Covid-19 in health care workers fell to 11.5% by late April, dropping 0.49% per day, on average.

In his editorial, Redfield made not only a public health case for face coverings but also an economic one. Citing an analysis by Goldman Sachs Research, he and his colleagues noted that if masking increased 15%, it “could prevent the need to bring back stay-at-home orders that would otherwise cost an estimated 5% of gross domestic product, or a projected cost of $1 trillion.”

“Broad adoption of cloth face coverings is a civic duty,” Redfield and his co-authors wrote in their editorial.

  • This is not about absolute isolation from viral components. First of all, this is not about viral contact it is about the viral load. It takes a lot more than one virus particle to get the disease or even be co soldered infected. It takes many many viral particles to be considered infected and many more to see symptoms. Reading the various medical responses just here on Stat about cracks in the process or suggesting that the direction of barriers and avoidance is correct is exactly why the USA has the highest rates of CV19 in the world. We are so hung up on being right we are willing to die for that process or worse kill others to prove the point
    To suggest that mask wear g is wrong because removal can expose the wearer to virus particles is as much malpractice as removing the wrong limb in surgery. Come on people this is not the annual flu season issue this has taken the lives of over 500k people and isn’t even close to being either under control or done with. Don’t think for one microsecond that as soon as the weather turns cooler than we aren’t going to see huge upticks in cases. Even with the promise of vaccines so far none have shown even remote even short term immunity so this is here to stay
    If you think you can out trick this or worse simply ignore it I bro g you to the realization like the youngster in Texas this last week who died from a CV party say g ” I think I really messed up”
    Stop trying to punch holes in why we should not be aggressive and start following the Southeastern Asian process of ”just do it and stop complaining”
    I don’t think we can afford to shut down fully again but we surely have to start to only go out when absolutely necessary and then only with barriers and avoidance in place
    Dr. D (medical advisor to the US Senate)

    • Dr. D – I am not disagreeing that we should wear masks but I have a bit of problem with the claim one particle of virus can not get you sick. There seems to be no good theoretical reason for that. And I see some scientists deny it, they claim you could potentially get sick from one particle or any virus.

    • Nice idea, Dr Dave, but sadly, you miss the point. The hypothesis that masks help, at ALL, is legitimate ONLY as an hypothesis. Yes, there is macro data that suggests it helps, but of course that ignores the ALSO questionable data that suggests it actually hurts in aggregate (remember, for 80 years the official opinion was that in aggregate, masks hurt in these circumstances). There was real scientific data to back that conclusion, unlike in the current situation.

      For example — as an alternate hypothesis — I might suggest that masks (unless made of a very effective filtering material) INCREASE aerosol virus clouds around an infected person. Prove me wrong!! After all, the person coughs material into his mask, then exhales — and that escaping air ecelerates through the cotton fibers to astonishing velocities — fibers that are soaked in virus infected water — and aerosolize the virus. Unless environmental effects degrade those virus particles quickly, we’ve just created a thick, virus infused cloud into which a non-infected person can walk and breath in many thousands of virus particles.

      Am I right? Heck, I don’t know. It’s an hypothesis that reasonable described the process. Let’s find out! But what I DO know is that YOU don’t know. You can’t explain why, 3 weeks after the Memorial Day protests, there is suddenly an explosion in cases — but it’s NOT a clear, 3 weeks after opening businesses, delay! So the meta-data actually push for my hypothesis.

      Yet you say we should mask up.

      Baloney. You’re a doctor, and presumably committed to “evidence based” knowledge. What happened to that objectivity?

    • Tom B. – maybe I do not understand all of your post – but you make some claims I have not heard, can you specify them?
      1. “Remember for 80 years the official opinion was that in aggregate, masks hurt in these circumstances” – what official opinion? Worldwide medical consensus? I have seen photos from the 1918 flu pandemic stating it was illegal not to wear a mask – they were in English, I do not know what country.
      2. Your claim that it is just an hypothesis that masks help seems to be challenged by reported studies – I can not cite them off the top of my head – recent studies, of countries which implemented masks wearing and saw big reductions in their new cases- they are not double blinded experiments obviously, so comparisons between those countries and other countries have to try to take into account other differences – but they do refute the claim the benefits of mask wearing are only hypothetical.
      3. You did not directly address this, and if your hypothetical greater aerosolization of virus particles is true, it could negate this effect – but it should not be forgotten, wearing a mask reduces the amount of virus a person will take in – they DO have a filtering effect – it was always considered too low to protect the wearer – but that belief was implicitly applied to hospital settings, with huge amounts of virus in the air- the question being answered with “No, non N95 masks do not protect the wearer was “Can non N95 masks keep our medical staff from getting sick?” -that is not the same as “Can non N95 masks worn by the public in all settings slow down or eventually stop and epidemic?””

      if I, Mr. John Q. Public, do everything else to reduce my chances of getting infected, and my own mask reduces that chance just another 50%, of no help in the CoV2 ward, where it might mean at best I get sick a few weeks later than I would have with no mask, the protective effect for me, exposed to virus once a week or less when I go to the store and get unlucky, may be more than enough to slowly stop an epidemic.

      But all this is not really addressing the problem correctly.

      There are filtering devices which greatly reduce the chance of infection – pressurized hoods where highly filtered air is pumped in, so that any non-filtered ambient air is pushed out. To these, suppressor filtering could be added, so that the wearer of the hood does not expel much contaminated air from exhalations or coughing.
      Or,alternatively, a simple homemade hood, non pressurized, prevents big clouds of aerosol from being expelled by a coughing person – and probably protects the wearer, as particle which will rapidly fall from the air will probably not make it under the hood.
      My point is, there is a lot of nonsensical debate over the face masks, rather than seeking to find and implement a technology which will work, pointless arguing over the deficiencies of the current one.

    • Steve, epidemiological evidence is NOT strong evidence for something, because there are so many possible alternative explanations for data that you see. That’s why researchers go back and study the actual physical processes to see if they can explain the epidemiological data. That’s what happened in 1939 — “are masks effective” and in studying what they could technologically at the time, they found through physical measurements that masks were very weak barriers but DID decrease large droplets spewing onto surfaces. It was a small enough effect that the CDC saw that the false sense of security it provided most people led to them doing infectiously dangerous things, which is why the CDC, the WHO, and MOST infectious disease experts were uniformly against mask-wearing for the past 80 years until — what? this June!! What changed? NOTHING. No one has studied aerosol effectiveness of masks in typical public use situations. NO ONE — and still, no one has. So, sorry, there is no SCIENCE. Again, hypothesis — guessing — only.

    • Tom, I understand epidemiological evidence is not considered as strong as controlled studies, but every Asian country, at this point, seems to have done much better than the US. For that reason, I am in favor of adopting all their control measures. And, very important, teaching our people how to adopt them properly. The problems you mentioned, except for aerosolization, seem to be due to bad technique.
      The simple reason for adopting all Asian practices is, they must be doing SOMETHING right – and, since they are all wearing masks, that can not actually be harming them much – if it was, they would have greater problems.
      Your thoughts?

    • Steve, I agree Asian country success suggests mask effectiveness, and following their lead seems very tempting. BUT. Those countries did what our CDC did NOT — they caught and contained infection before it spread. That, by itself, can explain 100% of the difference (and point out why we all should be so furious that our CDC was so inept). Once the horse is out of the barn, well, trying to do what they do is pretty meaningless.

      But, I wish we had answers. People keep bringing up the 1918 pandemic, but it was after that our national health officials figured out that masks were NOT effective — at least for flu. So, using 1918 as an example is quite silly, but it still doesn’t mean that masks are NOT effective. Or that they are!

  • I’ll participate in an experiment where ‘EVERYONE’ wears a mask 24/7 for 14 days straight. That should prove the masks are effective, but if Covid-19 is still around after that, shut up about the masks. It’s been 6 months, it’s not that hard an experiment to set up. In other news, masks do not form an airtight seal (the hot air blowing back at my face all day, leaves the mask), the air movement of one’s breath is only a minuscule component of the fluid dynamics causing the dispersal of suspended water droplets from exhaled breath. Would 100% enjoy being proven wrong.

    • Completely eliminate COVID-19 in 14 days? That’s an absurd standard and impossible even if masks were 100% effective at preventing transmission, unless they also actively cured people who were already sick. People don’t get better within 14 days of being exposed to the virus; many people don’t even have a positive test result back at that point. Meaning that the vast majority of people who were sick or exposed before your experiment would still be sick, or developing symptoms, and more importantly CONTAGIOUS, after the experiment was over.

      And that’s if masks are 100% perfect at preventing transmission. If they’re 99%, or 95%, or even 90%, they’d still be worthwhile despite failing your ridiculous test. That’s still a huge number of people protected from a serious and highly contagious disease.

    • Because only some people wear masks, it’s straight-forward to just observe transmission in people or populations where mask-usage varies naturally and infer the effect, and indeed this has been performed dozens of times during this pandemic. The efficacy likelihood is strong, it’s the bayesian priors people have against things they simply don’t enjoy doing that are causing all the hesitancy.

    • That was precisely my point, my ridiculous test would only be valid if masks are 100% effective. I doubt many would claim they are.

      If they’re 90% effective, how quickly would the infection be eliminated from an isolated population? Would it decrease the total number infected? Would it slow the progression? Would slowing the progression have an overall positive effect, or would it keep a perpetual supply of hosts (people) depending on how long recovered individuals retain immunity? Does a 90% effective mask affect the spread at all? These are some of the questions I’d like answered.

      I personally don’t mind some short-term discomfort for tangible long term benefits. To me, the current paradigm seems to be let’s just do “something” until there’s a vaccine. There’s a very real possibility there will never be a vaccine. We have a decent handle now on risk factors. It seems much more prudent to protect the more vulnerable than isolating the healthy.

      The disease is not nearly as deadly as initially thought, but is highly contagious. We’re able to contain small pox, I’m sure there’s a level of quarantine that is capable of controlling this virus. Trying to implement an effective level of quarantine (obviously more restrictive than the lock-downs in Mar/Apr) on the entire population would create tremendous pain. For the vast majority symptoms are mild to nonexistent. Letting the disease run it’s course is an option.

  • I find it interesting that you advocate the use of face-coverings yet cite no references identifying the risks in doing so. We have, for years, told patients to keep their hands away from their face during cold and flu season. This form of self-contamination has been identified as a major route of infection. I find it disengenuious that you would advicate such behavior without first looking at the potential impact and possible adverse response. Donning and doffing a contaminated mask is not risk free and considering most people reuse their masks these are highly likely to become disease vectors. More science is needed before we begin to proclam a failure of society to act.
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    • Dr. Rosenbaum:

      I am absolutely sure you are correct about the risks of donning and doffing the masks, and with reuse this gets worse – some people pull the masks off as soon as they can – like, they wear them into the store, pull them off – then handle many things in the store, that other people have likely handled – then put the mask back on with dirty hands.
      Without good technique, I am sure this happens. I have gloves and alcohol sanitizer in my pockets and try to use both if I have to touch the mask – generally, since I do not take it off until coming home, when i get home or to adjust it.

      But, I still believe, if other people wear masks, the chance they will infect me via the air is very low. They are not throwing out much virus.

      What I have noticed is, there is plenty of talk about masks and it is the order right now where i am – but not much instruction in how to do so properly.

    • And once again, what of viral particle size relative to the weave of the masks? As many experts point out this is like using a spaghetti strainer to cull out water impurities–illogical. I believe any benefit would be derived from the propensity for social distancing in mask wearers (although this too is far from universal) vs the physical viral “blocking” created by masking. I believe staying 1-2 meters away from others as potentially the most significant factor involved. NOT the masks.

    • Jen Kedra – the modern masks do not work like a sieve but you have a point, they do not remove all the virus either – but the apparent success in Asia suggests mask wearing is a big part of ending the epidemic.

  • CDC, Dr Fauci and the Surgeon General are now reaping what they sowed in March – when they repeatedly told the public masks are useless, stop buying masks. Months later, with no explanation of new data, other than the lack of transmission at the hair dresser, they tell people to wear masks. So far the only explanation, other than the statement from CDC today, is from Dr Fauci’s congressional testimony; testimony now interpreted to be that he lied to the public in March in order to protect the nation’s supply of medical masks for medical professionals. Were they all lying to protect medical supplies? They couldn’t say then that fabric is all that is needed for those not in direct contact with infected patients? Or is this just the unfortunate outcome of a new virus that has severe complications not expected from a respiratory virus? I tend to believe the later. But I find it hard to believe others do not understand why some of the public is now distrustful of the “experts”. Fortunately, since I had an almost 80yr old parent undergoing cancer treatment starting in February, I never believed any of them that masks would not have some protective benefit. So we were all masked even in the car when I drove him to appointments. And relied on physical distance in the home. I was wearing a mask in stores by the time we quarantined.

    • That is the point originally we wrongly assumed this was a typical virus and that kike seasonal flu it needed only basic precautions but now we know that it is airborne that paper masks aren’t enough and that masks alone aren’t enough in high-density areas like gyms and movie theaters, the WH depended on the facts and got political drivel to support their job status and now we are back doobking to keep their jobs while the admin tryies to be re-elected to keep the momentum of the past three years going to the best of its ability
      Can’t blame POTUS the most he can do is spout what he is told by experts and advisors and weigh it against the patty agenda. In this case, the party differed dramatically and the advice was really wrong. Dr. D

    • Amazon has them in multiple colors shapes and designs. Knock your socks off. We buy the cheap ones then go to Lowe’s and buy AC filter media marked HEPA and the strongest one then cut it up to fit in the included filter pocket each mask has as the filters they come with are NOT able to filter viruses but the HEPA material can

  • For a science-based newsletter, this report is utter garbage. Apocryphal stories and opinions of managers (no matter how many) is not science, and there are as many stories — in fact, vastly more convincing, to me — that clearly demonstrate mask-wearing (unless high performance masks) is of no to NEGATIVE utility. It does seem astonishing to me that everyone ignores the painfully obvious fact that the only real mask studies done date from 1939 and ONLY apply to large-droplet transmission, which appears to be minor in the case of covid19. And theories of aerosol generation even suggest that masks INCREASE the risk of transmission (which would make perfect sense if the extensive Memorial Day protests are the actual source of current increased transmission). Instead of perpetuating non-science, leaders — AND this newsletter — should be advocating for a relatively simple but truly scientific, evidence-based experiment of mask effectiveness.

    Oh, but I guess we’d rather this whole thing stays as “CDC-managed” opinion instead of evidence based medicine. Sure, why not? Who really wants to go back to work?

  • Why doesn’t the CRC recommend fining people who refuse to wear a mask which is proven to control Covid 19 virus? CDC needs to tell all the state governors to use their emergency powers to enact a time. Fines were instrumental in 1918 in stopping that Spanish flu. We need to learn from history.

  • I find it extremely comical that there are so many armchair quarterbacks trying to say what they would have done last winter or spring now that they have the ability to view what occurred via the rear view mirror. If the media would have steered clear of sensationalism and the minority party hadn’t feigned the end of the world without any solid data, we would certainly be in a better position now. Herd immunity will be kicking in soon if the data we have seen from Sweden holds. The south is seeing higher numbers now because they did what they were supposed to in the spring, FLATTEN the curve, while the northeast paid no heed and their numbers show it. Their numbers have run down so small as they are showing around 60% exposed.
    The entire mask issue may or may not be working. There are NO control groups to show any real evidence. We all hope that COVID acts like majority of other virus’ and ir burns out at around 20% HITS as it did on the carnival cruise ship. Stay safe, use common sense, and we will be done with this soon.

    • Tim, I am hoping this is the case also…..pretty much my observational analysis of this mess..

  • Too bad the CDC can’t apply enough pressure to the government and the public to wake up and mandate the use rather than this elective option. Sure everyone has freedom in the USA but freedom should come with responsible action. We don’t allow people to stand up in a crowded arena and yell fire without consequences why do we not enforce the use of PPE use when in public until this is under control? A rhetorical question as the answer is politics and the upcoming election cycle. Had this come out in 2021 it would be mandatory to wear masks but now the election is interfering with good science and good sense. Dr. D.

    • I am not disagreeing with you at all and I blame the Executive who discouraged masks more than anyone – totally irresponsible – he could have kept the country open with very high (and proper) mask use – BUT – it is not at all clear to me the Feds can mandate anything like this – so it goes back to individual states as best I an tell. Again, I agree with everything you wrote.

    • I’d like to add to Dr. Dave L’s good reasoning that the lopsided choices of “freedom” are being instigated by a deranged leader. If Trump were not president, masks would be worn and the virus would be long under control already. This President fails his flock, due to his total failure to accept advice from experts when it does not suit his “image” and his own selfish agenda.

    • BTW notice he said cloth masks not paper or paper towels or bandanas or some other strange face covering. He was specific in saying cloth (ie. Fabric MASKS) the effectiveness of properly designed masks is essential to the barrier. The USA population has spun the idea that this is a cursory no big deal issue and that as long as people stay separated and use minor barriers all will be well. Truly not factual. The WH is also in a Catch22 situation they spent 3 years building the economy only to then lose it to CV19 so surely they are trying g to balance the economy with biology. If the pandemic happened in January 2021 the WH would have accepted more scientific advice since the future of the USA wouldn’t be in as much jeopardy as it is right now. The DNC is spinning this as it’s the GOP’s fault when in reality it us China’s fault coupled with the American attitude of ”don’t tell me what to do” that has us where we are now. The mask situation is a perfect example. Even with common sense to wear masks people still soapbox about freedom and the government can’t tell them what to do etc… Even commentators here don’t believe that Uncle Sam should be allowed to mandate masks yet they are OK with some states saying yes. We need to get off the protection of the Constitution box and onto the protection of the citizen’s box otherwise, we will all be sick or dead. Dr. D

  • I am glad the CDC is saying this with absolutely no ambiguity. I am not a doctor or scientist but I believed this back in April, based on the online studies I was reading. There was another point which I think the CDC knew, and hid from us for a long time – though it is not as clear cut and one can debate what to do about it – it appears the rate of death or serious (known, immediate) complications is well under 1 in 1,000 in the over 5 but younger than 35 age group.
    I understand a very young person getting sick or dying would be much worse than an old person -but it appears we could have kept a large part of the economy going by ordering those over 35s and those with known risk factors to work from home, while the 18 to 34s did the high risk work – for a temporary raise paid for by the Feds. It would have required some very precise and strict temporary labor laws – and would not have saved the bars and restaurants -but been better than what we did.
    Because the emergence of zoonotic diseases may be much higher in the future, we need to institutionalize better approaches.

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