Here's everything we know so far.

While COVID-19 continues to spread across the country, experts still insist that the best way to help curb the number of cases is social distancing. But they’re also considering other precautions—and that includes possibly revising past recommendations.

Initially, major health agencies like the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) staunchly advised against mask use among healthy Americans in the general population—reserving the personal protective gear (PPE) like N95 respirators and surgical masks for those in the medical community on the front lines.

But now, “opinions on whether Americans should wear masks in public when running routine errands are evolving, because the situation in communities across the US is changing,” Julie E. Fischer, Ph.D., associate research professor of microbiology and immunology at Georgetown University Medical Center, tells Health.

According to original reporting by the Washington Post, the CDC is contemplating whether they should advise all Americans to wear face masks outdoors in order to add another layer of protection against transmission. The World Health Organization is also reportedly evaluating potential mask usage for the general public.

While the official recommendations currently continue to discourage mask use among healthy individuals, some US city officials, including the mayor of Los Angeles, have taken it upon themselves to urge individuals to cover up their noses and mouths when they head outside, according to Time.

So, should I start wearing face masks outside or not?

Clearly, that's a tricky question to answer right now, since official recommendations are up for review.

The biggest issue regarding mask use for the general public, according to Fischer, is that evidence suggests wearing face masks in public doesn’t necessarily do that much to protect healthy people from getting the infection—particularly for viruses that spread by droplets, like COVID-19.

That said, studies show that mask use among those infected with viruses—specifically the influenza virus in a 2009 study published in the Annals of Internal Medicine—can help prevent spreading the illness, when paired with proper handwashing, even among people in the same household. Further, one systematic review of various interventions during the 2003 SARS outbreak, published in the BMJfound that, while handwashing (more than 10 times daily) stopped virus transmission by 55%, mask usage stopped it by about 68%—and full protective measures (handwashing, masks, gloves, gowns) were 91% effective.

With new research finding that asymptomatic people can still transmit COVID-19, mask use may be important right now, even for those not showing symptoms. "We know now that people who are asymptomatic or who have mild symptoms can transmit the virus to others,” Fischer explains. “Wearing masks can help prevent transmission from infected people—who may not even be aware that they are sick—to others, which provides additional protection when combined with good hand hygiene and physical distancing.”

Regardless of whether masks are effective or not (and for whom), the biggest drawback of mask use right now is the shortage of PPE for healthcare workers who come in close contact with those with coronavirus and therefore, are at a much higher risk of getting the infection. “Preserving masks for those at the highest risk of being exposed or exposing others was the first priority,” Fischer says.

The N95 masks in particular provide the highest level of protection for those on the front lines right now, blocking out about 95% of even small droplets, according to John’s Hopkins Bloomberg School of Public Health. When N95 masks run out, health pros likely turn to surgical masks, which also feature a special material that blocks droplets, but unlike N95 masks, they don't seal the nose and mouth. (A 2019 study published in JAMA shows N95 and surgical masks can similarly block out influenza germs, but that may not be as true for COVID-19.) So it's probably in everyone's best interest to save these types for those actively fighting coronavirus.

Aside from the health implications, mask wearing may also provide some social cues. Mask wearing is already common in other cultures, like East and Southeast Asia. "People wear them as a sign of social responsibility to others—like, 'look, I'm protecting you from my infection'—and people who are well wear them to protect themselves when traveling or when they anticipate being crowded in close quarters," says Fischer. "During the current COVID-19 pandemic, mask wearing in those regions has been framed as a matter of civic duty; mask wearing is seen as a sign that individuals are willing to do their part to prevent asymptomatic transmission to others."

It's not as common to see people in the US wearing masks, and if people start to do it more often, it could either add or take away from the number-one precaution of staying away from others. "Right now, increasing mask wearing in the U.S. would be a powerful reminder to maintain distance—but people need to be reminded that mask-wearing is about them protecting others if they are asymptomatic," Fischer says. "If after a matter of days people become so accustomed to seeing others in masks that they start to think of them as protective and quit being vigilant about keeping their physical distance," then that could be dangerous, she adds.

Fischer adds that wearing a mask may also serve as a constant reminder not to touch your face—a key component in preventing infection of any kind. "A face mask can help remind people to keep their hands off their faces, and that might be one of the best outcomes from improvised masks," she says.

What if I decide to wear a face mask—what do I need to know?

First and foremost, it's important to remember that proper social distancing, self-quarantining, and self-isolation is still the best way to stop the spread of COVID-19. Also: healthcare workers on the frontlines still need PPE to do their jobs safely, meaning they need those N95 masks and likely surgical ones, too—so please don't go out and stock up on those now (though, you likely wouldn't be able to find any anyway).

That means, if you choose to wear a homemade mask (because, again, you should not be taking medical masks from those who need them), know that it's not necessarily a clinically protective effort. Fischer points to a recent report from respiratory and infectious disease experts at the University of Minnesota—the best evaluation Fischer has seen on masks to date, she says—that analyzes the research on masks. Essentially, it shows little evidence that wearing homemade masks can offer protection and may lead people to avoid social distancing. "Leaving aside the fact that they are ineffective, telling the public to wear cloth or surgical masks could be interpreted by some to mean that people are safe to stop isolating at home. It's too late now for anything but stopping as much person-to-person interaction as possible," the report reads.

If that still doesn't sway you from wanting to cover your face, Fischer says that household items, like scarves or other handmade masks, might block some droplets if you cough, though not as well as a surgical mask. “How effectively an improvised mask would prevent exposures would depend on the filtration capacity of the fabric and how closely the mask fits to the wearer’s face,” she says.

While there’s little evidence on how exactly to make an improvised mask, Fischer says the best results may come from heavier fabrics, like those you’d find in tea towels (those denser cloths that you might use to dry dishes), and those fitted as closely as possible to the face. Cotton T-shirt fabrics or the materials used in handkerchiefs don’t have as much filtering capacity to block out droplets, she says.

The WHO also offers tips for how to use and dispose of a mask properly, encouraging hand washing before putting on the mask and making sure there’s no gaps between your face and the mask when you have it on your skin. They also suggest you avoid touching the mask when it’s on your face (that will lead to contamination) and replacing it as soon as it gets damp. Also, to take it off, remove from behind first, toss, then wash your hands again. The critical step: Don't touch your face as you take the mask off.

“Wearing masks to prevent disease transmission would be one more tool, in combination with good hand hygiene, cough etiquette, and physical distancing measures, to slow disease transmission and prevent cases from peaking in communities all at once,” says Fischer. “While there is not a lot of data on the effectiveness of homemade masks now, researchers are asking questions that should offer answers soon.”

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDCWHO, and their local public health department as resources.

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