Update: The CDC is now recommending that all Americans wear non-medical cloth masks in public. President Trump says he will not.


Should you wear a mask in public in the age of coronavirus? The benefits of mask wearing by the general public is suddenly a topic of hot debate. The Centers for Disease Control has not recommended masks for masses, but that guidance is now under review as understanding of the spread of the coronavirus is changing. 

Most important, public health officials are learning that the virus can be spread by large numbers of asymptomatic and pre-symptomatic carriers — people who do not, themselves, feel sick and therefore don’t avoid public places.

There is also growing concern that the virus is not spread simply by heavy droplets — like those produced by coughing — that settle out of the air and onto surfaces, but may be spread by tiny droplets, emitted by speaking or laughing or singing, that can linger in the air.

In this time of crisis, N-95 respirators — tight fitting masks that filter out tiny particulates — should be reserved for medical staff. But science has shown that loser-fitting surgical masks can be effective as a barrier against sick people spreading viruses. The evidence that they prevent normal people, outside of a health care setting, from inhaling virus particles and getting sick is less robust. 

Public health officials are now weighing the benefits of encouraging masks to slow the spread of the highly contagious coronavirus — against the potential harm to the medical community, which is struggling to secure enough personal protective equipment for frontline workers. (Meanwhile a nation of makers and crafters and baseball uniform tailors is not waiting for guidance, and is already busy sewing makeshift masks, including from templates published in the New York Times, despite concerns that home-crafted masks may not be effective.)

To help sort through this confusing calculus, Rolling Stone reached out to Donald Milton, both a medical doctor and doctor of public health, who runs the Public Health Aerobiology, Virology, and Exhaled Biomarker Laboratory at the University of Maryland. Several years ago, Milton published a paper showing the potential effectiveness of surgical masks in limiting viral spread. But as he spoke to Rolling Stone, Milton was mostly angry that the United States has so utterly botched the response to this pandemic that generalized mask wearing has become part of the conversation. He noted that a country like Singapore has managed to contain the spread of the coronavirus through robust public health measures, which have allowed its economy to keep functioning while reserving masks for the medical community and the obviously ill. He also points to South Korea that got ahead of the pandemic through mass testing. “We have that capability,” he says, “We could have done that.” Because we didn’t, Milton says, “We’re totally behind the 8-ball here. So we’re desperate.”

Rolling Stone: Everyone is trying to understand the impact of mask wearing by the public — to what extent do they help people avoid getting sick? Or is the idea that they they could help with people who may not know that they’re sick avoid broadcasting virus?
Donald Milton: The last point is really important. I had a paper in PLOS Pathogens in 2013 on the effects of surgical masks on shedding of [influenza] virus. What we found was, yes indeed, if you wear a surgical mask it will knock out about 25 fold of your coarse aerosol — droplets bigger than 5 microns. It really massively reduced the amount of virus in the coarse aerosol. And it reduced the fine aerosol by 2.8 fold — a little less than two thirds, or by more than half. 

I’ve been hearing a lot about droplets and aerosols — does the difference matter?
There’s a tendency to talk about droplets and aerosols as if they’re qualitatively different things. They’re actually a continuum there’s no cutoff. 

So just tinier and tinier droplets — and some float and some fall to the ground?
It’s a dynamic process. It depends what environment they’re in — how dry it is in the air. The infectious disease medical community talks about them as though they were different things, as though there were a bright line between the two. No such thing exists. 

So masks could make a difference?
If you’re talking about something that might make a little bit of difference in the community, if everybody did it, and we could knock it down by half — that’s not going to get us the R-naught below one. But you can make an argument that every little bit is important. And in the current situation we’re desperate.

[Editor’s note: a virus’s reproductive number, or R0, pronounced “R-naught”, is a measure of contagiousness; the R0 value for the coronavirus, absent social distancing, is between 2 and 3, meaning each person infected with the virus would be expected to pass it on to two or three other people. Lowering the R0 below 1 would cause the outbreak to begin to subside.] 

So the idea is to tamp down on the broadcast of the virus rather than prevent an individual from inhaling virus particles? Or does it work both ways?
It is going to capture stuff that is otherwise coming into your lungs, so it might do a little bit on the recipient. I think it does less on the recipient. It’s going to do more on the source.

We’re learning that you can be shedding this virus without knowing that you’re contagious. So it could be helpful to put on a mask, so you’re not spreading it everywhere as you’re going about your business?
Visiting your elderly parents, you don’t know whether you could be infected. You should do this.

How did we end up in this fix?
We weren’t prepared. We’re still not prepared. We’re totally behind the 8-ball here. So we’re desperate. Because the things we are doing are horrible. We’re throwing people out of work, with all kinds of untoward consequences of being unemployed — it’s very toxic to your health. Heart attacks. You get depressed. People hurt themselves, hurt other people. All of that happens. So this is a terrible solution that we’re seeing. So you could make the argument that we should try everything.

People are pointing to the use of masks in Asian countries that are doing a better job of controlling the spread of the virus.
Masks are not being used, however, in Singapore in the general public. They’re saying, “Reserve surgical masks and respirators for health care workers,” and they’re still controlling the virus. Their first community case, their first introduction of COVID-19, was on the same date as the first introduction in the United States.

You look at how many cases they’ve had. [Editor’s note: Singapore has roughly 1,000 cases.] Now it’s still going up. And they’ve had a few deaths this week. But they controlled it because they made massive investments in public health infrastructure that we didn’t make. We laid off public health workers in the Great Recession and we didn’t hire them back. We disbanded our pandemic response planning unit at the White House. And you know, Make America Great Again — we’re number one in COVID cases. 

To play devil’s advocate, Europe is obviously having an even worse go of it than we are. And if you look at the places that have succeeded in tamping down the spread of this virus, they are either peninsulas or islands. I wonder, in a country as big and porous as ours, was it inevitable that we’d end up eventually with an outbreak like this?
No, I don’t think so. I think South Korea being a peninsula and Singapore being an island has no bearing. Look at the number of airborne-particulate isolation rooms in Singapore. I was there in September, and they have a purpose-built hospital for dealing with pandemics. They opened it last summer with 120 high-level rooms and another 300 single-bed standard isolation rooms. Just amazing the investment they made. 

The reason Singapore, Taiwan, South Korea, and Hong Kong did so well is that they got slammed by SARS, and in South Korea MERS, where they had people waiting in line, shopping around for ERs, trying to get tested. And in the process those people infected a lot of other people. So [after that], they prepared. In Singapore they haven’t had masks for the general public. They’ve had school closures. And they did things like use the national university’s dorms to isolate people. They apparently have enough public health workers that they can very intensively follow the contacts of every case and make sure they’re getting isolated and tested. 

You think we could have — with a robust investment in public health — avoided this disaster?
Avoided this economic disaster that we’re creating? Definitely. This is not the only way to do public health. Singapore is showing a way. South Korea: They massively rolled out testing, instead of, like, waiting for the perfect test and going through regulatory hijinks. We’re just barely starting to get testing rolled out now because it’s taken this long to get FDA approval. 

We didn’t unleash our biomedical establishment to create tests. Every molecular virologist I knew had a test weeks before the CDC did. It’s sort of a hobby to come up with better detection methods. It’s a friendly competition. Everybody in January was like, “Oh, I can make my assay work.” Then a group in Berlin published theirs and WHO said, “Ok those are ours.” I have an assay in my lab that ThermoFisher produces that does great. I’m not a clinically approved lab, so I’m not allowed to test people for diagnosis, but I use it in my research. So I test people for my research. 

But [the U.S government was] funnelling everything through one portal [the CDC] and not letting anybody else jump in there and test because, [they said] we don’t know what the false-negative and false-positive rates of these tests are, and you don’t have FDA approval, so we can’t do anything.

South Korea, what I understand, said screw that! They said we have to get out in front of this or we’re going to have the same problem we had with MERS. So they turned their biomedical industry loose, and they started producing lots of tests right away. And they just started testing the heck out of the place, and within a couple of weeks they were running 10,000 tests a day. And they had a big problem. Because they had a ton of imported cases going into that religious group, that had a branch in Wuhan. So you know, it was tough. If we’d had that number of introductions here, holy smokes. 

So the point being that South Korea not only tested early, but they had to contend with a huge hot spot early on, and they still managed to get out in front of it?
They wasted no time and got right on it. Unleashed their testing their molecular biology industry capability to crank out tests. We didn’t do that. We have that capability. We could have done that. 

So what exactly happened? I read a story in the New York Times that the CDC had a test for three markers of the virus, and only two worked well, and they got stuck on that. Until they decided that two markers were good enough?
That was part of it. And then they said nobody else is allowed to test. Seattle — Dr. Helen Chu. You probably saw that New York Times article. [Editor’s note: The piece describes how the Seattle Flu Study uncovered community spread of COVID-19 by testing flu swabs they’d already collected for the coronavirus. Federal officials then shut down that activity.] The same thing happened to a lot of other people.

Other people trying to test got shut down?
We were trying to test people here who’d come back from Wuhan. And we got told by the state tisk tisk, naughty naughty. Can’t do that. You’re not a clinical certified lab. 

So regulations in place, ostensibly to protect people from shady operators, in fact prevented our full capacity from coming online?
Right. In normal times it’s a rational thing. But in normal times everyone wearing surgical masks is not a rational thing either. 

Was the testing the critical issue?
Testing by itself doesn’t work either. You need the workforce to do the contact tracing. When you lay off huge fraction of the public health workforce you’re basically disarming. It’s like deciding all of a sudden you’re going to have no Army.

And those layoffs happened mostly around the Great Recession?
In the Great Recession, state and county budgets were clobbered, and where did they save money? Public health people. The numbers I’ve seen are that since about 2006 there have 55,000 jobs reductions in the public health workforce at the state and county level. They reasoned as long as they’ve still got a one or two people left to keep the restaurants from poisoning us we’ll be OK, right?

Extraordinary how much we spend on defense and how little that expenditure actually defends us.
And then there are issues of infrastructure. Why do we have to shut down the schools? Because people are close together or because there’s no ventilation in elementary schools? It’s been known for years that schools are the major source of spread for influenza. We didn’t do anything about it.

Since social isolation started, there’s been a lot of “outdoor shaming” — criticizing people for biking and hiking and going to the beach. Is it risky being outside?
If people are close together, it’s going to be risky. When you’re speaking, your puffs can enter someone else’s breathing. That can happen outside. If there’s no breeze, or you’re downwind. It’s like if someone was smoking a cigarette and you’re downwind of them. If they were exhaling the virus, and you’re downwind…. Outdoors is not perfectly safe.

I get worried when I see people piling into Costco and Trader Joes — that seems more disturbing to me than people out on the beach or a hiking trail. They look more at risk to me, but what do I know.
I would think so. But again, if you’re packed together outdoors in a stadium or a rock concert or spring break…. And especially if you think about what people do at sporting events, they yell and scream and they’re generating a lot of aerosol. 

To return to mask question. Obviously masks are in short supply and there’s a worry about putting the general public in competition with the medical workers who desperately need masks. Does a bandana do something?
Somebody tested household materials and how they capture. Vacuum cleaner bags are the best but hard to breathe through. The key is, how do you make it filter efficiently but not have a lot of flow resistance, because the more flow resistance there is the more you breathe in from around the sides — and that doesn’t do anything.