If everyone in the US wears a mask in public, 33,000 lives could be saved over the next 3 months, one model suggests

• US coronavirus cases are rising sharply in 29 states.
• A growing body of evidence suggests a mask-wearing requirement could stymie the virus' spread significantly.
• The University of Washington's infectious-disease model projects that by October 1, more than 179,000 people in the US could die from COVID-19 — 57,000 more than have died already.
• But if 95% of the population were to wear face masks in public, the projected number of deaths falls to 146,000.

With 29 states reporting increases in new coronavirus cases — and some breaking daily records — it's clear the US's coronavirus-prevention strategy isn't robust enough.

One public-health measure is increasingly being cited as a way to significantly prevent the spread of the virus if deployed on a national scale: face masks.

A growing body of research indicates that contrary to information put forward early in the pandemic, masks do prevent coronavirus transmission. On Wednesday, the widely cited coronavirus model from the University of Washington's Institute for Health Metrics and Evaluation's updated its projections to assess the benefits of mask wearing.

The IHME publishes forecasts predicting the country's coronavirus cases and deaths, constantly tweaking them based on how the epidemic curve changes and which preventive measures, like social distancing or mask requirements, are put in place.

The latest model predicts that by October 1 more than 179,000 people in the US will die from COVID-19. So far, more than 122,000 people have been killed by the virus, so the forecast expects 57,000 more deaths in three months.

Those numbers are based on current social-distancing measures and rates of mask wearing. But when the model took into account how transmission might change if 95% of the population were to wear face masks in public, the number of projected deaths fell to 146,000.

"There is no doubt that even as states open up, the United States is still grappling with a large epidemic on a course to increase beginning in late August and intensifying in September," the IHME's director, Christopher Murray, said in a statement. "People need to know that wearing masks can reduce transmission of the virus by as much as 50%, and those who refuse are putting their lives, their families, their friends, and their communities at risk."

States could save lives with mask requirements

The IHME's models also estimate how mask requirements might change the course of specific statewide outbreaks.

Take Florida, for example, which does not have a statewide mask mandate, though a few counties do. If Florida continues on its current trajectory, according to the IHME model, there would be nearly 15,400 COVID-19 deaths by October 1. Currently, the coronavirus has killed 3,300 people in the state. But if 95% of all Floridians started wearing masks now, the prediction falls dramatically, to 7,500 deaths by October 1.

Compare that with California, where Gov. Gavin Newsom started requiring all residents to wear masks last week. The coronavirus death toll in California on October 1 is projected to be 11,600. With even more widespread mask use, the projected death toll would drop to 8,700.

Both the US Centers for Disease Control and Prevention as well as the World Health Organization recommend that people wear cloth face coverings in public settings, especially in areas with significant community spread.

But in the absence of national policy in the US, states have been implementing varying mask requirements in a piecemeal fashion. At least 38 states have instituted some sort of mask requirement: In California, Delaware, Illinois, Maine, Maryland, Massachusetts, Michigan, New Mexico, New York, Rhode Island, Utah, and Virginia, the mandate applies to all residents who go outdoors.

Other states, like Oregon, Ohio, and Pennsylvania, require masks for workers at local businesses. In North Carolina, masks are recommended but not required for the general public, though cities like Raleigh and Durham require them outside.

According to an analysis by The Philadelphia Inquirer, coronavirus cases seem to be rising overall in states with relaxed face-mask rules. By contrast, The Inquirer found that new cases had fallen by 25% in total over the past two weeks in states that mandated masks in public.

On aggregate, the states that require mask wearing by both employees and customers at local businesses (depending on the state, those rules might apply to restaurants, retailers, or personal care) have seen a 12% drop in cases. Indiana, Pennsylvania, and Washington all fall on that list. States that require masks only for the employees of certain businesses, however — that includes Florida, Georgia, and Nevada — have seen a 70% increase in new cases, on average.

A growing body of evidence indicates that masks prevent coronavirus transmission

In Springfield, Missouri, last month, two hair stylists at the Great Clips salon tested positive for COVID-19. They had seen 140 customers since the salon reopened. But of the 46 customers tested, none were positive.

The likely explanation for this lack of transmission was that all employees and customers had worn masks.

"Which mask worked, the hairdresser's or the client's? I think the answer is yes. They both worked," Robin Trotman, an infectious-disease specialist in Springfield, told The Washington Post.

Masks make a difference because coronavirus particles pass between people in tiny droplets of saliva and mucus. If a sick person sneezes, coughs, talks, or eats within 6 feet of someone else, the particles could land on them and enter the eyes, nose, or mouth. That's how infection spreads. So a mask that covers our nose and mouth helps block those particles.

"It does have some protection for the wearer," Dr. Ramzi Asfour, an infectious-disease doctor in the San Francisco Bay Area, previously told Business Insider. "If you think about somebody sneezing on you, there's a lot of these droplets that come out. Well, a lot of those droplets are big and they'll easily be stopped by the mask."

Other case studies have found benefits of mask wearing. Recent research from UK scientists found that the more people who wore masks in a community — even if the masks were only 50% effective at blocking the virus — the closer the community could get to containing its outbreak, even without a lockdown.

"These results are striking in that the benefits accrue to the face mask wearer as well as to the population as a whole," the researchers wrote. "There is, therefore, a clear incentive for people to adopt face mask wearing."

Another study from Indian researchers found that infectious droplets traveled about three times as far when a person wasn't wearing a cloth mask — up to 16 feet, compared with just 5 feet when particles leaked out the sides of a face mask.

Dr. Anthony Fauci said during an interview with the Sacramento Press Club last week that politics shouldn't get in the way mask requirements.

"It should not be a political issue. It is purely a public-health issue," he said. "Forget the politics. Look at the data."

Aria Bendix contributed reporting.