Just wear masks already, America. It's a small price to pay for saving lives.

In late May, two hair stylists at the Great Clips salon in Springfield, Missouri, tested positive for COVID-19. Between them, they'd seen 140 customers since the salon reopened. They could have been contagious the whole time. But instead of detecting a cluster of new cases, local public-health arrived at a surprising finding: Of the 46 salon customers tested for the virus, not one was positive .

The most likely reason: All salon employees and patrons 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 . "The system worked. Universal masking worked."

Indeed, a growing body of research shows masks can that prevent coronavirus transmission.

A recent study from UK researchers found that requiring individuals to wear face masks all the time could be enough to contain an outbreak on its own, no lockdown necessary. The more people wore masks, the researchers determined, the closer a community could get to containing its outbreak.

"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."

But in recent months, groups of "anti-maskers" have protested against policies that require face coverings. Some argue that it impinges on their freedom, while others question the science behind it.

As evidence continues to mount in support of mask-wearing, there is no more room for this debate. Americans across the country must wear masks within 6 feet of one another or risk endangering more lives.

Yes, masks prevent transmission

Even if people wear masks that are only 50% effective at trapping infectious particles when they breathe, universal adoption of masks would still stop an outbreak, the UK study found.

That research aligns with findings from Arizona State University , which showed that "broad adoption of even relatively ineffective face masks may meaningfully reduce community transmission of COVID-19."

The university's models in April determined that if nearly everyone in New York state wore a mask, that could prevent up to 45% of projected deaths over two months even if the masks were only 50% effective. In Washington state, the model found, face masks that were only 20% effective but worn by most of the population could still reduce mortality by up to 65%.

This information, by now, shouldn't be remarkable. We know respiratory droplets are the primary method by which people pass the coronavirus to others. A mask that covers our noses and mouths blocks those particles.

"It does have some protection for the wearer," Dr. Ramzi Asfour, an infectious-disease doctor in the San Francisco Bay Area, 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."

Indeed, Indian researchers recently determined that a simple cloth mask "substantially decreases" the spread of virus particles when an infected person coughs or sneezes. According to their study, infectious droplets traveled about three times farther (up to 16 feet) when a person wasn't wearing a mask, compared to just 5 feet when particles leaked out the sides of a face mask.

An April study in the journal Nature also showed that surgical masks reduced the transmission of multiple human coronaviruses (not including this new one, SARS-CoV-2) through both respiratory droplets and aerosol particles.

Contradictory guidelines sewed confusion among Americans

It's understandable that people are confused about whether or not masks really help, since all this evidence wasn't available at the start of the year. Unfortunately, that's when public-health officials had to make quick calls about whether people should be required to wear masks in public. Authorities also had to stockpile enough personal protective equipment for healthcare workers, which meant masks were in short supply.

At the start of the pandemic, the US Centers for Disease Control and Prevention did not recommend the use of face masks for the general public. Other public-health experts, including those cited by Business Insider in February , also advised that the practice was unnecessary outside China.

The recommendations were delivered at a time when the risk of infection in the US seemed low. Now the country has the world's worst outbreak, with more than 2.1 million cases and 118,000 deaths.

Back in February, scientists also hadn't learned about asymptomatic or pre-symptomatic cases, which are now understood to make up around 35% of coronavirus infections .

"I have anger that we didn't know in March that we should all wear masks," Lilly, a physician in Westchester who tested positive for the coronavirus in April, told Business Insider. She requested to go by a different name due to her job. "If in March or, even better, in February somebody told us to wear masks and social distance, then I may not have gotten the disease."

In response to new data, the CDC began recommending face coverings in settings where it's difficult to maintain social distance starting April 3.

But the World Health Organization sewed more confusion a few days after that, when the group said there was no need for healthy people to wear face masks . The WHO then reversed its decision and began recommending face coverings on June 5.

mask coronavirus REUTERS/Caitlin Ochs

Some public-health experts continue to disagree about whether masks should be a requirement for the general public. When Business Insider recently put the question to 15 leading public-health experts , 11 said masks should be worn, three were uncertain, and one said no.Robert Beardall, who cast the lone dissenting vote, said his answer stemmed from worries that homemade masks would provide a false sense of protection and lead people to get too close to one another.

But research now suggests that wearing masks improperly or sporadically could still reduce transmission and homemade masks are better than none.

Masks have become politically divisive

On May 14, a group of 100 medical and scientific experts wrote an open letter asking governorsto require cloth masks in public places, including stores, transportation systems, and public buildings. The requirement, they wrote, "could be amongst the most powerful tools to stop the community spread of COVID-19."

But many local leaders haven't enforced this mandate and those who did faced opposition from residents.

The chief health officer of Orange County, California, Dr. Nichole Quick, resigned last week after receiving threats over a mandate she issued that required residents wear face masks in public. On May 1, a security guard in Flint, Michigan, was shot and killed after asking a dollar store customer to wear a face mask. A few weeks later, a man in Portland, Oregon, was filmed yelling at a grocery-store employee who had asked him to wear a mask inside.

Across the country, protesters have rallied against mask requirements. On May 1, the day San Diego instituted its mask rule, hundreds of protesters gathered outside a local courthouse without face coverings. Some of them held signs saying "Science is fake news" and "Trump 2020." At an April rally in Austin, Texas, protesters also called for an end to the city's mask requirement.

A protester holds up a sign protesting wearing a mask at the Texas State Capital building on April 18, 2020 in Austin, Texas. Sergio Flores/Getty Images

Trump said in an interview with the Wall Street Journal on Thursday that he believes some Americans wear face masks to show their disapproval of him. Trump has repeatedly been photographed without a mask at public events.

Mask requirements are inconsistent across the country

Cheyenne Beyer, a 27-year-old coronavirus patient who lives in Austin, said she's worried that people who ignore mask requirements may wind up infected like her.

"My boyfriend has gone to the grocery store and the convenience store a couple of times in the past few weeks, and that even worries me because even though he wears a mask, so many people here aren't," Beyer told Business Insider. "At my infectious-disease doctor appointment today, there was a guy in the waiting room who wasn't wearing a mask at all. And then the other people in the waiting room were wearing masks, but they had their noses exposed."

Mask guidelines aren't consistent across states or counties. At least 38 states have instituted some sort of mask requirement; in California, Massachusetts, New York, Utah, Delaware, Maine, and Michigan, the mandate applies to all residents who go outdoors. Other states, like Oregon and Ohio, require masks for employees at local businesses. In North Carolina, masks are recommended for the general public, but certain cities like Raleigh and Durham require them to be worn outside.

Austin's mask requirement is still in place, though residents can't be penalized for forgoing a face covering, since the policy isn't mandatory in Texas. The city's mayor, Steve Adler, has said the penalty for not wearing a mask is simply that "more people are going to die."

States with mask requirements also offer exemptions for residents with medical conditions like asthma or chronic obstructive pulmonary disease (COPD), though people don't need to provide documentation of these illnesses because of patient privacy laws.

The problem with this piecemeal approach, however, is that the absence of a unified national policy has turned masks into a political statement instead of what they are: an effective public-health tool.

"It's how others take responsibility for protecting you," Dr. Asfour said. "By not wearing a mask, I'm not doing my duty to protect others."

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