Some experts in an increasingly loud chorus are criticizing federal recommendations that Americans stay 6 feet apart from each other to stop the spread of the novel coronavirus.

Richard Corsi, a Portland State University dean, has studied the spread of COVID-19 through both large and tiny droplets in the air and recommends people stay 20 feet away from each other when they’re outdoors.

Indoors, where ventilation is much worse, Corsi recommends extreme caution and carrying out essential tasks like grocery shopping when truly necessary.

What do he and a small group of aerosol science colleagues across the nation think about the 6-foot social distancing advisory from the U.S. Centers for Disease Control and Prevention?

“It’s just been driving us nuts,” Corsi said.

“I don’t think we’re being safe enough,” he said. “People need to understand that the airborne route, that’s a serious transmission pathway.”

Corsi’s advice is bolstered by a study published last week in the Journal of American Medicine by a Massachusetts Institute of Technology researcher. It found that the virus can travel as far as 27 feet indoors when somebody sneezes and remain floating in the air for hours, waiting for the next person passing by to breathe it in.

Sneezing droplets can travel up to 8 metres - keep your distance!



High resolution images #Covid19 #SocialDistancing

Source : Lydia Bourouiba, JAMAhttps://t.co/nyq64bdQz3 pic.twitter.com/j0HqXs81jk — Pascal Meier,MD (@DrPascalMeier) March 30, 2020

Scientists also say the virus -- encapsulated in saliva and mucus droplets as tiny as 1/200th the width of a human hair – can enter the air when someone talks or even breathes.

A study in the New England Journal of Medicine recently found the virus could linger in the air and still be infectious three hours later.

This week, the CDC said as many as 25 percent of people infected by the new coronavirus don’t show any symptoms and spread it unknowingly as they circulate in the community.

That, in turn, led the federal agency on Friday to reverse its position on masks and recommend all Americans wear face covering or homemade masks.

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Guided signage asks for customers to stay 6 feet apart for social distancing when waiting to checkout on April 2, 2020. (Lisa DeJong/The Plain Dealer) Lisa DeJong/The Plain Dealer

Still, the CDC is standing by its 6-foot separation advisory -- for the time being. Leagues of public health officials also have said for the past month that the distance should suffice, and that when someone sneezes or coughs their droplets quickly fall to the floor within the 6-foot distance. They’ve also said the virus can spread through touching contaminated surfaces.

The 6-foot recommendation has had a big impact on precautionary measures taken in many parts of the nation and in Oregon -- from grocery stores putting down tape markings on their floors to governors issuing stay-at-home edicts.

Gov. Kate Brown used the guidance to structure her stay-at-home order March 23, closing businesses where “close personal contact is difficult or impossible to avoid,” including shopping malls, athletic clubs and hair salons.

But she allowed businesses that aren’t specifically listed to remain open, as long as they could keep employees or customers at least 6 feet apart. The governor also said exercise or gatherings are OK as long as people maintain at least 6 feet of space.

The Oregonian/OregonLive asked the Governor’s Office if the latest findings will prompt Brown to change her order. Spokeswoman Liz Merah said the governor hasn’t made any decisions as of Friday, but “all options are on the table.”

“Things are rapidly evolving and we’re making the best decisions we can with the data and evidence we have available at the time, in consultation with public health, epidemiologists, and medical experts,” Merah wrote in an email.

A spokesman for the Oregon Health Authority, Jonathan Modie, said in an email Saturday that “there are no plans to change or reconsider the distance guidance at this time, and we won’t be elaborating.”

A spokesman for Portland Mayor Ted Wheeler said the mayor wasn’t planning tighter restrictions.

“We will look first to our partners and public health officials at the state and Multnomah County to provide guidance about social distancing,” the Mayor’s Office said in a statement.

But some public health officials elsewhere appear to be acknowledging that they’ve misunderstood how the disease spreads.

In Washington, stunned Skagit County health officials told The Los Angeles Times that they are almost certain tiny particles suspended in the air are responsible for a large COVID-19 outbreak at a March 10 choir practice in Mount Vernon, 60 miles north of Seattle. Two people have died from the disease and 45 have fallen ill. At the time, no one who’d attended the choir practice at Mount Vernon Presbyterian Church reported any symptoms.

The World Health Organization has offered a much looser guideline for safe social distancing than the CDC -- telling the public it should remain 3 feet from others who don’t share the same household.

That has elicited even stronger objections from some aerosol scientists who have been busy posting their criticisms on social media.

“People are disturbed that some of us are saying the virus could travel further than 6 feet because it goes against the WHO,” tweeted Kimberly Prather, chair of atmospheric chemistry at the University of California San Diego. “(WHO’s) recommendation is based on research done in the 1930's.”

Prather this week urged Southern California surfers who are defying California’s shelter-in-place order to stop crowding the waves for a while. Ocean breezes, she said, can blast the virus from the mouth of one surfer into the next.

The same goes for runners who stride next to one another across the sand or bicyclists who ride one behind the other on the roads, she said.

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That’s difficult advice to hear, in the time when more than half of the world is under some sort of lockdown order and humanity is craving social interaction that doesn’t involve an electronic screen.

Corsi, the PSU dean, said we should all be creating more space between us -- not just during an essential trip to the grocery store or pharmacy, but while outside recreating.

Even though the outdoors has more air flow and “turbulent mixing” that can blow away and disperse droplets, the virus still can infect others, especially on a calm evening with no wind, he said.

When someone coughs, large droplets of mucus and saliva fall to the ground relatively quickly, but microscopic particles also are ejected and float through the air.

If you’re near that person, you could be in trouble -- even though you’re outdoors, said Corsi, who also serves as president of the International Society of Indoor Air Quality and Climate.

That’s why he recommends 10 feet of outdoors distance if no one is coughing, but said 20 feet is even better because someone might suddenly start coughing.

Corsi described a simple trick to maintain a proper distance: “If you’re going outside, pretend everybody’s a smoker and you don’t like cigarette smoke.”

Setting a lawn chair out in the yard or driveway and visiting with a neighbor is OK as long as it’s 20 feet, Corsi said.

But the equation changes with friends wanting to join up for a run.

He recommends letting 10 seconds pass before you cross the pass of another person, including your running buddy. Runners in particular breathe heavily and could potentially be expelling more of the virus into the air, he said.

And the idea of hiking on one of the region’s many narrow trails -- like Portland’s popular Wildwood Trail -- becomes an all-out terrible idea if it involves passing other people trekking the opposite direction, he said.

If an oncoming hiker coughs just before you pass, “you’re probably walking through a cloud of viruses that stay suspended in air,” Corsi said.

If an oncoming hiker says “hello” that also increases the chance they’re propelling the virus into the air, he said.

Indoors, the risks increase dramatically, Corsi said, “because someone can cough in one room and these small particles can easily migrate throughout the entire house.”

Corsi recommends going outside the house and into other indoor spaces -- such as a grocery store -- as seldom as possible.

“If word had gotten out a month and a half ago -- ‘You need to stay indoors’ …’Don’t go out in crowds. Don’t go out to the bar. Don’t go to the coffee shop’ ... that probably would have saved a lot of lives,’” he said.

Stay safe! Protect yourself & others by practicing physical distancing whether indoors or outdoors. Avoid indoor environments other than home and essential services, e.g., grocery store. Stay connected with others remotely. Stay calm. We'll prevail if we don't let down our guard. — Dr. Richard Corsi (@CorsIAQ) March 18, 2020

As for face masks, Corsi said the new advisory shouldn’t lull people into a false sense of security. People must still remain an adequate distance from others.

DIY face coverings might protect large aerosolized droplets from infecting others, but they won’t stop tiny droplets from getting inhaled.

The fabric is too loosely woven and the coverings don’t form a tight seal around the face.

Staying at home, Corsi said, “is your effective N95 mask.”

-- Aimee Green; agreen@oregonian.com; @o_aimee

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