Why hundreds of scientists are asking WHO to say the coronavirus is 'airborne,' and why WHO isn't jumping to do so

• A group of 239 scientists is asking the World Health Organization to acknowledge that coronavirus-spreading events generally share three qualities: they happen indoors with large crowds sharing the same air.
• WHO has been hesitant to say the coronavirus can be "airborne," which would mean it could float in the air farther than a few feet.
• The agency maintains that the coronavirus spreads mainly via respiratory droplets, which, though a fraction of the width of a human hair, are heavy enough that they tend to fall to the ground within 3 to 6 feet of their host.
• But the group of scientists warns that evidence suggests the virus can spread much further indoors in poorly ventilated spaces.

The novel coronavirus has spread at bars, in elevators, at churches, and at restaurants, meatpacking plants, karaoke parties, nursing homes, prisons, and just about anywhere else crowds of people gather indoors and breathe.

"We know that the biggest risk is these closed, indoor environments," a University of Maryland virologist, Don Milton, told Business Insider.

Milton, along with hundreds of the world's leading virus scientists and environmental engineers, is pressing the World Health Organization to better convey to the public how this virus behaves in the air.

Enclosed indoor settings in particular are thought to have played an important role in spreading the virus, and the disease it causes — COVID-19 — around the world.

Until now, WHO has maintained that there's no evidence the virus can stay aloft in the air for very long or travel very far in it outside hospital settings.

But the scientists behind this new letter say that may not strictly be the case when you're in a stuffy space. As a result, they say, WHO's position that airborne transmission is not a concern for the general public is no longer airtight.

"It's increasingly clear that these big outbreaks where lots of people get infected are one of the most important ways in which this pandemic keeps going," Milton said. "We need to stop those superspreading events, and the way to stop those superspreading events is to pay attention to airborne transmission."

WHO has stuck to an old-fashioned definition of 'airborne'

WHO stresses that the coronavirus does not typically float, with the exception of a few clinical "aerosol generating procedures" in hospitals (including intubation, ventilation, and resuscitation).

"Airborne transmission is different from droplet transmission," WHO says in its most recent guidance on the subject, because airborne virus "can remain in the air for longer periods of time, and can be transmitted to others over distances greater than 1 meter," or roughly 3 1/3 feet.

Why hundreds of experts are calling on WHO to change its messaging

On Monday, Milton and the coauthor Lidia Morawska were among an international group of 239 scientists who put their names on an open letter in the journal Clinical Infectious Diseases, titled "It is Time to Address Airborne Transmission of COVID-19."

The letter was meant to get the world's biggest public-health organizations "including the World Health Organization" better on board with the idea that the coronavirus spreads easily through the air from person to person — even, perhaps, up to "several meters" away across a room.

They stress that is one big reason the pandemic virus continues circling the world, and they say the public should be aware as restaurants, bars, clubs, and offices open up.

"There's real concern that delay in pushing the idea of universal masking and talking about transmission by aerosols, airborne transmission, has put people at risk, and that there are fairly straightforward things that people could do to be safer and to reduce the spread of the virus," Milton said.

The agency is listening but is cautious about making big statements

On Tuesday, WHO still said more research was needed to know for sure how this virus spread best.

The health agency said it would be issuing a "scientific brief" on the subject in the coming days in the wake of Milton's recent letter.

"We have been engaged with this group since April, when they first wrote to us on April 1st, and we've had an active engagement with them," Maria Van Kerkhove, WHO's technical lead for the coronavirus pandemic, said Tuesday during a press conference from the agency's headquarters in Geneva.

But the agency is taking a cautious approach.

"Any guidance that we put out has implications, of course, for billions of people around the world. So it has to be carefully considered before it is done," WHO's chief scientist, Soumya Swaminathan, said Tuesday during the briefing. "We want to be as fast as possible, and adaptive and responding to the new evidence. And at the same time, we have to consider the weight of the evidence."

Fresh air can help make indoor spaces less dangerous

WHO has so far maintained that this virus spreads best when people cough, talk, breathe, and sneeze out contaminated droplets — which are a fraction of the width of a human hair but much larger and heavier than aerosols, which float in the air.

Droplets spread from person to person through close contact, especially when people are together for extended periods of time.

From a layperson's viewpoint, it may not seem that important to know whether the virus spreads through droplets or aerosols, as both contain tiny little doses of virus.

But the distinction subtly changes your risk perception of everyday actions and may change how close people decide to get to others when indoors during the pandemic.

Give the public better information about the powers of crowd control, masks, and airflow

Better crowd control, more masking, and paying close attention to air quality in closed, heavily trafficked spaces are three critical ways to stop this virus as we continue to learn more about how it spreads and make mundane decisions about how to proceed with everyday life in the absence of a vaccine.

"We have to learn to live with this virus," WHO's executive director of health emergencies, Mike Ryan, said last week, encouraging "every person" in the world to "take control of your own destiny."

Likewise, Dr. Anthony Fauci, the US's top infectious-disease expert, told members of Congress last week that "we need to emphasize the responsibility that we have both as individuals and as part of a societal effort to end the epidemic — that we all have to play a part in that."

If the general public is paying closer attention to air flow, crowding, and wearing masks, this will all be easier.

"It's really trying to grapple with what we know is happening and doing very simple, straightforward things that we can do that can stop the spread of this virus," Milton said.

"By not having too many people sharing the same air, and by not putting a lot of virus into that air, we can keep these events from happening."

But Milton and his colleagues are worried that WHO's current message leaves out some "fairly straightforward" ways the virus has been transmitted in recent months, especially when big crowds gather indoors. They stress there's room for some more precautions, in conjunction with the handwashing, social distancing, mask wearing, and quarantining recommendations already in place.

"We're not saying that the things that have been recommended are wrong — we're just saying there's more stuff to be done and that it's important for people to know about it," Milton said.

3 ways to prevent superspreading events

According to Milton, three measures are key to prevent transmission of a virus that "needs a lot of people, breathing the same air," and "somebody contaminating that air with virus."

1. Making sure indoor spaces are better ventilated, including opening up windows and doors to bring in outdoor air, and maintaining good air filtration in closed spaces, minimizing recirculating air.

Both the American Society of Heating, Refrigerating and Air-Conditioning Engineers and the Federation of European Heating, Ventilation and Air Conditioning Associations have guidance on this.

2. Avoiding overcrowding in public spaces.

3. Using germicidal UV lights overhead to kill the virus. Milton's lab uses these in places where researchers work with people who have the coronavirus, and he's not worried about any of them getting infected.