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Science Has No Clear Answers On The Coronavirus. Face Masks Are No Exception.

Over the course of the last week, America somehow went from being a country where very few people were willing to wear masks for health … to one where regular people are trading mask-making patterns like sourdough starter.

But the messaging about mask usage remains muddled. That’s true for the Centers for Disease Control and Prevention, which updated its public recommendations to include wearing masks whenever you go out in public on the same day President Trump announced he would not be wearing one. It’s also true in the scientific community, where dueling experts both urge widespread public face mask usage and dismiss face masks as useless and potentially dangerous.

Meanwhile, those of us with sweet, loving mothers who like to craft their way through anxiety are rapidly accumulating stockpiles of homemade masks. (I currently have 10 masks, and I have been told that another boxful is on the way. Thanks, Mom!) So what are we — the suddenly cloth-mask-owning people of America — supposed to take away from this? Is it a good idea to wear a mask in public?

That’s a trick question, experts told me. And we actually need to be asking something altogether different. “I would say there’s a lack of evidence to support either position,” said Benjamin Cowling, professor of epidemiology and biostatistics at Hong Kong University. “When we have a lack of scientific evidence, then we have to use our judgment on what might be the best thing to do and what’s at stake.”

And judgment is subjective: It’s influenced by personal experience, by how people view risks and benefits, and by how they weigh the balance between the two. Sometimes, we have to make big, serious decisions, even when research hasn’t conveniently supplied us with absolute, unequivocal facts. We’re in the land of uncertainty — a place that the novel coronavirus pandemic has forced us to visit a lot lately. Masks are just one part of it. And the question isn’t, “Should we wear them or not?” It’s, “How do we make a decision when there isn’t an answer?”

Uncertainty is hardly unfamiliar for people who work in public health. “That’s a normal day in the life for most of us,” said Lara S. Martin, a former program manager at Emory University’s Center for Humanitarian Emergencies. She’s done public health research in the field of humanitarian response for over a decade. But making life or death decisions in the face of big question marks is not the norm for millions of average Americans, who are struggling to understand everything from how long they should wash their hands to how many people are likely to die from the novel coronavirus this year.

The mask debate is part of that big picture of uncertainty. We just don’t have data, even for the efficacy of medical-grade masks in protecting against the transmission of a fluid-based virus like Ebola. The more specific the question becomes — What about cloth masks? What’s the best filter? How airborne is coronavirus, exactly? — the more hazy the data. There are studies on these issues, experts told me, but there’s not enough data to be conclusive. About the best anyone can say is that, depending on several variables like the type of mask and how well it’s used, there’s probably a small benefit to wearing masks — in preventing the wearer from spreading the virus to others.

But that still leaves plenty of space for reasonable experts to reasonably disagree. Martin and Cowling come down on opposite ends of the face mask debate. Martin, who said she has watched misuse of masks and gloves spread disease in emergency situations, believes masks can create a false sense of security. After all, we know of other times where safety measures have led people to take more risks — not fewer.

Meanwhile, Cowling — who said he has lived through multiple epidemics in Hong Kong and seen successive waves of public health campaigns improve the way the public uses masks — believes the very limited evidence of a small potential benefit to public health means it’s worth doing. To him, the risks of wearing masks can be mitigated, and every small benefit stacks on top of the last.

“People are saying, ‘Why do it with no evidence?'” Cowling said. “And others are saying, ‘Why wouldn’t you do it if there’s no evidence?’”

Sometimes — pretty often, actually, in medicine — people have to make decisions even when there isn’t enough data to tell them what to do. There are even situations where finding more evidence can, itself, be harmful, said Michelle Driedger, professor of health sciences at the University of Manitoba. Take lower back pain, for instance. Faced with a patient who is in pain and wants to know what’s wrong, a doctor might be tempted to order some kind of imaging test, she said. “But sometimes that’s a soft tissue issue, where rest is better than exposing ourselves to X-rays, because they can’t necessarily identify if there’s really a problem, anyway,” Driedger said.

Common sense doesn’t always apply. And you have to be prepared to update your choices as more information comes in. Be prepared, in other words, to get comfortable without knowing the correct answer right now, and get comfortable with knowing your answer may change in the future. You also have to accept that changing your mind about how to fight the pandemic doesn’t mean you’ve failed. “It will change. This is just the way we learn and adapt,” Martin said.

At the end of the day, experts told me, when evidence is lacking, individuals and public health officials alike have to make a call based on what we do know, our personal experiences and our own understanding of risk and risk management.

Cowling and Martin agree that if Americans start wearing masks, it’s vitally important that they are explicitly taught how to use them. We’ve gotten some helpful suggestions for how to make simple, cheap masks at home, which is crucial if we want to avoid encouraging people to snap up N95 masks that health care workers need.

But Cowling and Martin say Americans also need detailed information on how to make and wear masks in a way that maximizes the benefit to them and minimizes the risk. That’s going to require videos, advertisements and an all-out push to teach and change behavior, they both said. Until that exists, Martin’s advice is to imagine that, every time you use a mask, there’s something really disgusting that’s gotten on it and that it’s plainly visible. “If you could see it, and it was gross, what would you do? You wouldn’t touch it. You wouldn’t wear it again. You’d wash it in the hottest water you can with strong detergent. Some of that can help,” she said.

Ultimately, the expert advice on masks (and hand-washing, and death tolls, and the proper distance to keep between yourself and others, and … and … and) is to get comfortable with not knowing the right answer. You can (and should) have some trusted advisors. You can (and should) read up on why certain things are or aren’t being recommended. But there are a lot of issues around this virus on which two experts can read the same data and come to different conclusions.

For the rest of us, that means accepting that, sometimes, we’ll just have to do the best we can without a clear set of instructions. “That’s one of the best gifts we can give ourselves,” Martin said.

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Maggie Koerth was a senior reporter for FiveThirtyEight.