Effectiveness of Surgical and Cotton Masks in Blocking SARS-CoV-2: A Controlled Comparison in 4 Pati

[sl8]

From https://annals.org/aim/fullarticle/2764367/effectiveness-surgical-cotton-masks-blocking-sars-cov-2-controlled-comparison

Effectiveness of Surgical and Cotton Masks in Blocking SARS–CoV-2: A Controlled Comparison in 4 Patients

LETTERS | 6 APRIL 2020

[...]

Background: During respiratory viral infection, face masks are thought to prevent transmission (1). Whether face masks worn by patients with coronavirus disease 2019 (COVID-19) prevent contamination of the environment is uncertain (2, 3). A previous study reported that surgical masks and N95 masks were equally effective in preventing the dissemination of influenza virus (4), so surgical masks might help prevent transmission of severe acute respiratory syndrome–coronavirus 2 (SARS–CoV-2). However, the SARS–CoV-2 pandemic has contributed to shortages of both N95 and surgical masks, and cotton masks have gained interest as a substitute.

Objective: To evaluate the effectiveness of surgical and cotton masks in filtering SARS–CoV-2.

Methods and Findings: The institutional review boards of 2 hospitals in Seoul, South Korea, approved the protocol, and we invited patients with COVID-19 to participate. After providing informed consent, patients were admitted to negative pressure isolation rooms. We compared disposable surgical masks (180 mm × 90 mm, 3 layers [inner surface mixed with polypropylene and polyethylene, polypropylene filter, and polypropylene outer surface], pleated, bulk packaged in cardboard; KM Dental Mask, KM Healthcare Corp) with reusable 100% cotton masks (160 mm × 135 mm, 2 layers, individually packaged in plastic; Seoulsa).

[...]

Discussion: Neither surgical nor cotton masks effectively filtered SARS–CoV-2 during coughs by infected patients. Prior evidence that surgical masks effectively filtered influenza virus (1) informed recommendations that patients with confirmed or suspected COVID-19 should wear face masks to prevent transmission (2). However, the size and concentrations of SARS–CoV-2 in aerosols generated during coughing are unknown. Oberg and Brousseau (3) demonstrated that surgical masks did not exhibit adequate filter performance against aerosols measuring 0.9, 2.0, and 3.1 ?m in diameter. Lee and colleagues (4) showed that particles 0.04 to 0.2 ?m can penetrate surgical masks. The size of the SARS–CoV particle from the 2002–2004 outbreak was estimated as 0.08 to 0.14 ?m (5); assuming that SARS-CoV-2 has a similar size, surgical masks are unlikely to effectively filter this virus.

[...]

This experiment did not include N95 masks and does not reflect the actual transmission of infection from patients with COVID-19 wearing different types of masks. We do not know whether masks shorten the travel distance of droplets during coughing. Further study is needed to recommend whether face masks decrease transmission of virus from asymptomatic individuals or those with suspected COVID-19 who are not coughing.

In conclusion, both surgical and cotton masks seem to be ineffective in preventing the dissemination of SARS–CoV-2 from the coughs of patients with COVID-19 to the environment and external mask surface.

[...]

[Squinch]

1. They don't stop the cough from escaping, but if I am healthy and wear

a mask, will it keep me from getting sick as a result of these particles we are learning about that stay in the air long after the sick person has passed? I know this doesn't address that, but that is my question.

[janterry]

2. Several factors here:

we believe that the concentration of viral exposure matters. It's basically a race for the virus to replicate in your body and your immune system to beat back the virus.

The more exposure you have seems to matter. So, even a cloth mask will help limit that. It filters something.

We are still trying to figure out the particles that linger in the air - and potentially affect you in (say) 2 hours (the big droplets from a sneeze drop very quickly - and that is what healthcare workers are most in danger of when working closely with a patient).

however, it's the aerosolized particles that hang around for up to 3 hours that have captured everyone's attention. The cloth mask can provide some protections from that (it's not an N95, but it is a filter). But it would not filter all of that out, no.

So, cloth mask might minimize your exposure to those aerosolized particles. It would be foolish protection in an ICU (of course).

The overarching problem is that we don't know the denominator for this illness - so we don't know how quickly it is spreading. We know how many of us have severe symptoms (check those hospital numbers). But we don't know how many have minor - or even moderate symptoms

and no idea how many of us are carriers with no symptoms. Until we know that - we're all guessing.

However, if aerosolized particles were hanging around in a supermarket for 3 hours - long after the very loud talker (spitting in air) or sneezer left the market. We might think that many millions of us would be sick. That r 0 value would be much higher. Every person would infect lots and lots over several days.

Of course, without widespread serology testing (and understanding that denominator) - we're pretty blind in all of this. So, it's a guess.

At the end of the day, my mask provides YOU protection. (In case I have it and don't know).

(Information coming from watching multiple JAMA interviews with MD's who are on the front lines of research and treatment of Covid

[Squinch]

3. Thank you for such a thoughtful answer.

There is SO much we don't know about it, but your observation that many more would be sick if the loud talker or the panting runner on the park path were spreading it is logical and comforting.

The fact that you point out, that we don't know the denominator, fills me with anger, though. There's no good reason for that.

[janterry]

5. It makes me very angry, too since

it's not just important to understand spread - it's also our only exit strategy.

Lock downs are very primitive mechanisms - when you have nothing else - lock everyone down.

Fine, we did that. Then what?

How can we get out of lock down if we don't know who is a carrier --and who has built up immunity.

The next step is to slowly release the population (after we get past our curve). Fine, who do we let out?? If we test everyone - like Germany, we know who is safe to return to work.

I would PAY out of pocket to see if I'm safe (shouldn't come to it, but at this point, I don't care). I might even pay quite a bit.

But the fact is, that test is really inexpensive (from what I read only 10/test)

I don't have a twitter account. But it seems to me #serologytesting needs to go viral. It should be the second question at every presser (after where the f is the ppe and vents?).

[Squinch]

6. I would pay too. I want to know, but also plasma from recovered patients

seems like it has been an effective treatment.

So we say let's get more of that.

But we can't.

Because, once again, testing.

And Filthy Donnie says AT A PRESS CONFERENCE! AS A GOVERNOR TELLS HIM THAT TESTING IS A PROBLEM! that he hasn't heard that testing is a problem.

[Igel]

7. Germany's up to about 1% of the population tested.

We're at 0.6%.

That's assuming (1) all tests, positive and negative, have been reported (we know that's false for the US, so 0.6% is too low); and, (2) each kit represents one person tested, so people didn't get repeat tests.

Comparison reality with something romanticzed always makes reality look bad.

New Jersey is just behind Germany for tests/1 million, and New York is at 1.6%. So NY is *ahead* of Germany. So saying testing is why Germany is so low and no testing is why NY is so high doesn't work, unless we pitch time into it--Germany started testing earlier. And it's worth noticing that Germany's a few days behind us for deaths/1 million population--it's where we were a few days ago. And a few days ago it was where we'd been a few days before that.

[janterry]

8. I want that serology test, though

not the + or - antigen test (serology will test for +/- AND whether or not you had it (and did not know - and are now, likely - immune)

[Karma13612]

4. Interesting.

I would like to have seen studies on more patients. Further, to really explore real world scenarios for people having to face the virus in their own lives, I would like to see studies done in public places.

Using a negative pressure room is fine for hospital scenarios, but not real life for the rest of us needing to go food shopping.

In a negative pressure environment, when you cough, would the droplets be pulled away from the lungs and be forced out into the room?

Also, they did admit there were more particles on the outside of the masks than inside.

Anyway, thanks for the info.
Still wearing a mask to the store!!