Minnesota Gov. Tim Walz this week is poised to issue a statewide order requiring everyone to wear masks or face coverings in various public settings as a way to control the spread of the coronavirus. Nothing was definite as of Friday.

If he does, Minnesota would join at least 23 other states with statewide mask mandates — and an expansive list of nations worldwide comprising more than 90 percent of humanity. Disney World reopened on Saturday — with masks required for all. It would also fill in what is rapidly becoming a patchwork of mask requirements in some communities but not others. St. Paul, Minneapolis, Edina, Rochester, Mankato and Winona are among the growing list of communities with mask requirements for everyone in certain public spaces, often with an emphasis on indoor areas where distancing can be difficult.

Such a requirement would signify the statewide climax of what has amounted to a reversal of policy for Minnesota and much of the western world, where public health officials in the early days of the pandemic advised strongly against wearing masks.

Months later, as evidence of the benefits of widespread masking has mounted, the chorus of those urging mask use has swelled to nearly overwhelming proportions. Advocates range from the Mayo Clinic to the U.S. Centers for Disease Control and Prevention, from Minnesota Health Commissioner Jan Malcolm to Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.

In fact, it’s hard to find anyone with medical expertise and credibility who will advocate against widespread wearing of at least cloth face coverings. That group appears increasingly to consist of a scattered figures on the political right who decry government mandates, and, based on feedback received by this reporter, some who plain don’t like wearing them.

While the World Health Organization has remained reserved in its recommendations, it does not stand against the practice in areas with community transmission, which includes much of Minnesota. And the agency is expected to revise its recommendations in the coming weeks as doctors press it to get on board, as happened Friday when the WHO acknowledged — at the urging of 239 scientists — the possibility of airborne spread of the coronavirus by people who don’t know they’re infected. That’s a key factor in the reasoning behind mask mandates.

“We support people using them. They should use them. We should throw the kitchen sink at this, and it (mask wearing) causes no harm.”

That’s what Dr. Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy, told the Pioneer Press on Friday. Osterholm, the former state epidemiologist, has been among the most visible of those who have pointed to the gaps in our knowledge of masks and COVID-19, but he emphasized Friday that those who have cited him as opposing masks have taken his recent statements out of context.

Osterholm and numerous experts contacted for this story bemoan the politicization of mask-wearing — a phenomenon that appears almost unique to the United States — and President Donald Trump’s refusal to publicly wear a mask until this past weekend or to strongly endorse their use among the general population. That political divide, however, seemed to shift earlier this month when several largely red states in the Sun Belt witnessed skyrocketing infection numbers.

“Medical studies have shown that wearing a face covering slows the spread of COVID-19 and it protects you and your family,” Texas Gov. Greg Abbott said July 2 when he ordered all Texans to wear face coverings in public. That was a reversal for Abbott, a Republican who had previously limited local governments’ ability to enforce local masking requirements.

But was Abbott’s assessment correct? How much do we really know about the effect of widespread masking on a virus that humanity only discovered this winter?

THE LOGIC: SOURCE CONTROL

The strongest case for everyone to wear masks is that many of us could have the virus and not know it — and we could spread it by speaking, breathing, shouting, coughing, singing and any other means by which small virus-laced droplets or particles are ejected from our mouths. Masks of various styles can block many of those particles, making its spread less likely — and perhaps less severe — to those around us.

The rationale behind requiring them with the force of law is that, at least across much of America of late, simply asking people to wear them doesn’t seem to be working. Allowing the maskless to mingle, the reasoning goes, infringes on the rights of others to safely go into necessary public spaces such as grocery stores.

To be clear: Mingling should always be avoided. Experts emphasize that keeping your distance from others is likely the most reliable way to protect yourself and others.

But won’t masks give us a false sense of security and cause us to mingle more? No one knows for certain, but some evidence actually suggests the opposite.

One study in Italy found wearing a mask actually caused people to give each other a wider berth when passing on the sidewalk. In fact, the more homemade the mask looked, the more distance strangers gave to the mask wearer. And here’s the capper: If you add a pair of goggles to your wardrobe, people keep even farther away. Goggles aren’t believed to provide significant protection for the general population in casual settings, but the keep-away-from-that-weird-looking-guy factor might be powerful, the researchers concluded.

Some mask supporters theorize that wearing masks might keep us all mindful that nothing is normal, that this is a time for caution. But, like many theories on the fringes of mask-wearing, there doesn’t appear to be hard science on that.

But there’s a lot of evidence pointing to the benefits of a masked population.

WHAT WE KNOW, HOW WE KNOW IT

“We know it works because we can literally see it,” said Jeremy Howard, a research scientist at the University of San Francisco who started Masks4All, a growing affiliation of scientists who have been urging mask mandates for months.

Howard was referring to the physics of masks and how imaging with the aid of lasers allows researchers to see how face coverings can block droplets from ejecting out of our mouths when we speak.

Do we know that these physics prevent infections from spreading? Not conclusively.

Such a study would involve subjecting healthy people to the shouts and coughs of people known to be infected with a potentially fatal disease with no surefire treatment — an ethical nonstarter. There’s also a rabbit hole of specialized science and semantics that gets into aerosols versus droplets that this can lead you down. Those supporting masks say that misses the point: even if cloth masks aren’t 100 percent effective, they save lives.

Because here’s something else we know: Countries with widely followed masking requirements have seen significantly lower transmission than those where fewer people wear masks. In one study that attempted to control for other variables, such as stricter lockdown measures and age, per capita deaths were more than 10 times lower in masked countries.

Like much of the science of COVID-19, that study has not completed its peer review process, so it’s hard to present such findings with the confidence scientists normally demand.

There are also studies from China showing that in a home setting, wearing some sort of face covering, combined with frequent hand washing and distancing, reduces spread among family members.

We also know that fears over shortness of breath or carbon dioxide buildup are unfounded for most people.

“That’s really bogus,” said Dr. Priya Sampathkumar, head of infectious disease for the Mayo Clinic in Rochester, Minn. She notes, for example, that asthmatics sometimes wear masks to filter out smoke particles to help them breathe. “People with heart failure or lung disease, sure, there can be concern. But not for most people. In health care, we’ve been wearing them for decades.”

The Mayo Clinic has required masks for everyone on its town-like campus for months. Compliance has been between 93 percent and 98 percent among patients, and transmission levels among patients and staff have plummeted from the early days, she said.

WHAT WE DON’T KNOW

What mask is best? Surgical, cloth, what fabrics of cloth masks?

In short, we don’t know.

“We think surgical masks probably work better but we don’t know, and we don’t have enough of those anyway, so we recommend cloth masks,” Sampathkumar said.

Howard of Masks4All said material choices are unclear — and it would be good to know since some evidence suggests something as simple as a paper towel can strengthen a mask’s filtering properties. “To my frustration, no one is doing the research in the academic fields to figure out which accessible materials and designs work well,” he said.

Fundamentally, we also don’t know how much of the virus one needs to get — and thus how much contaminated air — to get sick. Because of that, the whole masking endeavor will be shrouded in a level of uncertainly, Osterholm said. “We still don’t know how well they work,” he said.

PROTECT THE WEARER?

There’s a potential secondary benefit of masks: It’s possible that even cloth masks could provide some protection for the mask wearer.

“We think it might lower the viral load so people who get infected while wearing masks don’t get as sick,” said Sampathkumar, who cares for COVID-19 patients in intensive care at Mayo. “That’s my experience.”

Is that definite? “No, it’s not quantified, but it’s observational.”

HARD SCIENCE HARD TO DO

“These are things we cannot prove, unfortunately,” said the Mayo’s Dr. Vincent Rajkumar. “We just can’t do randomized studies in the midst of a pandemic.”

Rajkumar was the lead writer on an open letter to state governors and world leaders that summarized the body of science and urged mask mandates. It was signed by more than 100 scientists and doctors.

Rajkumar isn’t an infectious disease expert. He’s an oncologist. Like many doctors-turned-maskivists, he said he found himself brainstorming with other doctors, including his wife — Sampathkumar — who is an expert. The evidence became clear months ago and has only grown since, he said.

But his expertise in cancer treatment isn’t irrelevant, he said. “As an oncologist, I’m often faced with a patient who doesn’t fit neatly into a study, and you have to weigh the risks with the benefits.

“With masks, you have to weigh the risks and the benefits: What if we find out two years from now that it would have helped, and we could have saved hundreds of thousands of lives but we didn’t do it? On the other hand, what if we find out that it was a big waste of time? Well, we wore masks for a while and it was uncomfortable. That’s it.”

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