Wear a mask for you! (Yes, and other people, too)

There’s been lots of good and appropriate messaging on masks as source control to help prevent pre-symptomatic (a huge portion) and asymptomatic Covid spreaders from unknowlingly transmitting the disease to others.  And we’ve been told, unless you are wearing an N95, it’s probably not going to do too much to protect you.  But, increasingly some experts are thinking that, yes, even cloth masks (and definitely surgical masks) can play a vital role in preventing you from getting sick.  Not actually contracting Covid, mind you, but actually make it far more likely you’ll have a case with very mild or no symptoms.  I’ll take that!

This LA Times article sums it up nicely [and for those of you on twitter, I think this thread does even better and describes and links to a lot of the most compelling evidence, culminating in this tweet

https://twitter.com/DrEricDing/status/1286388906636845060 ]

Anyway, back to the Times article:

What’s the point of wearing a cloth face covering if it doesn’t filter out everything?

Cloth face masks still provide a major protective benefit: They filter out a majority of viral particles.

Embrace your floof, Bodie! That STAINMASTER® PetProtect® carpet is made to resist pet hair, so it’s no problem when you shed those beautiful golden locks.

As it turns out, that’s pretty important. Breathing in a small amount of virus may lead to no disease or a more mild infection. But inhaling a huge volume of virus particles can result in serious disease or death.

That’s the argument Dr. Monica Gandhi, UC San Francisco professor of medicine and medical director of the HIV Clinic at Zuckerberg San Francisco General Hospital, is making about why — if you do become infected with the virus — masking can still protect you from more severe disease.

“There is this theory that facial masking reduces the [amount of virus you get exposed to] and disease severity,” said Gandhi, who is also director for the Center for AIDS Research at UC San Francisco.

What evidence supports this theory?

The idea that a lower dose of virus means less severe illness is a well-worn idea in medicine.

Even going back to 1938, there was a study showing that by giving mice a higher dose of a deadly virus, the mice were more likely to get severe disease and die, Gandhi said.

The same principle applies to humans. A study published in 2015 gave healthy volunteers varying doses of a flu virus; those who got higher doses got sicker, with more coughing and shortness of breath, Gandhi said.

And another study suggested that the reason the second wave of the 1918-19 flu pandemic was the deadliest in the U.S. was because of the overcrowded conditions in Army camps as World War I wound down. “In 1918, the Army camps [were] characterized by a high number of contacts between people and by a high case-fatality rate, sometimes 5 to 8 times higher than the case-fatality rate among civilian communities,” the study said.

Finally, a study published in May found that surgical mask partitions significantly reduced the transmission of the coronavirus among hamsters. And even if the hamsters protected by the mask partitions acquired the coronavirus, “they were more likely to get very mild disease,” Gandhi said.

What happens if a city dramatically masks up in public?

If Gandhi is right, it may mean that even if there’s a rise in coronavirus infections in a city, the masks may limit the dose of virus people are getting and result in less severe symptoms of illness.

That’s what Gandhi says she suspects is happening in San Francisco, where mask wearing is relatively robust. Further observations are needed, she said.

There’s more evidence that masks can be protective — even when wearers do become infected. She cited an outbreak at a seafood plant in Oregon where employees were given masks, and 95% of those who were infected were asymptomatic.

Gandhi also cited the experience of those aboard a cruise ship that was traveling from Argentina to Antartica in March when the coronavirus infected people on board, as documented in a recent study. Passengers got surgical masks; the crew got N95 masks.

But instead of about 40% of those infected being asymptomatic — which is what would normally be expected — 81% of those testing positive were asymptomatic, and the masks may have helped reduce the severity of disease in people on board, Gandhi said.

So, wear that damn mask!  I must say, I find this very encouraging as I contemplate 75 minutes twice per week in an indoor space (half capacity, all wearing masks) starting in a few weeks.  Even better, I’m going to take my surgical mask up to near N95 efficacy with “Fix the Mask.”  Surgical masks actually filter almost as well, their major issue is fit, but with a little DIY rubber you can pretty much replicate that fit.


About Steve Greene
Professor of Political Science at NC State http://faculty.chass.ncsu.edu/shgreene

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