Is the Coronavirus Airborne? The Debate Between Scientists and WHO Explained

Over 200 scientists have called on public health bodies including the World Health Organization (WHO) to recognize that the coronavirus that causes COVID-19 is "airborne."

The debate centers around organizations such as the WHO focusing on SARS-CoV-2 (the name of the coronavirus that causes COVID-19, not to be confused with SARS disease) spreading in large droplets from coughs and sneezes that quickly fall under gravity, and preventing the spread of disease from surfaces though handwashing, as well as maintaining social distancing.

It also partly comes down to a technical discussion over what the term airborne means, which some say may confuse members of the public.

Below we explain what the signatories claim, the different definitions of "airborne," and what the discussion means for the average person trying to protect themselves and others from COVID-19.

'It is Time to Address Airborne Transmission of COVID-19'

On Monday, 239 scientists from 32 countries signed a commentary entitled, "It is Time to Address Airborne Transmission of COVID-19" published in the journal Clinical Infectious Diseases.

The experts argued there is "significant potential" that microscopic droplets could pass viruses on at short to medium distances, "up to several meters, or room scale."

Studies demonstrate "beyond any reasonable doubt" that viruses released when an infectious person exhales, talks, or coughs, microdroplets small enough to float in the air are released, and risk infecting people beyond 1 to 2 meters (3.2 to 6.5 feet), they wrote.

Signatory Julian W. Tang, Honorary Associate Professor in the Department of Respiratory Sciences at the University of Leicester, told Newsweek via email: "If you can smell your colleague's garlic, alcohol, curry on their breath after lunch, you are inhaling some of the air that they are exhaling."

In a typical indoor setting, these small droplets can travel "tens of meters, much greater than the scale of a typical room, while settling from a height of 1.5 meters [4.9 feet] to the floor."

SARS-CoV-2's genetic material, thought to have been spread by such small droplets, has been found in the air in some research, and the virus has been shown to still be infectious at this size, the team said.

The signatories went on to criticize the numerous international and national bodies which, when advising the public on how to avoid spreading and catching SARS-CoV-2, focus on hand washing, maintaining social distancing, and being cautious about droplets when coughing and sneezing.

"Most" public health bodies, including the WHO, don't recognize airborne transmission except in specific medical settings, they said.

According to the signees, this focus is not enough to protect people from infected microdroplets. This problem is most concerning in enclosed environments, particularly where there are crowds and poor ventilation, depending on the number of people and how long they are exposed.

"Admittedly," the evidence on every step in the spread of SARS-CoV-2 in microdroplets is "incomplete," but that is no different to theories surrounding the spread from large droplets and surfaces, the academics wrote. These routes of transmission work in parallel with one another, and yet the airborne aspect isn't widely recognized, they said.

There is "more than enough" evidence to persuade leaders that precautions should be taken against airborne spread, particularly as there is no vaccine to protect against COVID-19, the scientists wrote.

Tang said: "The WHO should demonstrate that aerosol transmission is not happening—rather that we (the scientists) should demonstrate that aerosol transmission is happening."

The signatories led by Professor Lidia Morawska, an expert on air quality and human health at Australia's Queensland University of Technology, and Donald Milton, Professor of Environmental Health at the University of Maryland School of Public Health, laid out a series of recommendations in their article.

These include: ensuring public buildings, workplaces, schools hospitals and care homes are properly ventilated; supplementing this with equipment that removes contaminants from the air, such as air filtration devices, and germicidal ultraviolet lights; and avoiding overcrowding, particularly in public transport and public buildings.

Simply opening both doors and windows in a building can "dramatically" increase air flow, they said.

Not acknowledging the risk "will have significant consequences," they wrote, as people may falsely believe they are protected based on current guidelines.

The issue is particularly important as countries are re-opening their economies, and citizens return to work and education after lockdowns.

They concluded: "We hope that our statement will raise awareness that airborne transmission of COVID-19 is a real risk and that control measures, as outlined above, must be added to the other precautions taken, to reduce the severity of the pandemic and save lives."

A WHO spokesperson told Newsweek the article will be addressed at a press conference on Tuesday.

What do we mean by 'airborne'?

Confusingly, airborne in this context doesn't mean the same as it does for other diseases such as measles and tuberculosis, where viruses can spread easily over long distances. Ian Jones, professor of virology at the U.K.'s University of Reading in England, who was not involved in the article, told Newsweek SARS-CoV-2 is "not truly airborne."

Professor Jose Vazquez-Boland, Chair of Infectious Diseases at the U.K's University of Edinburgh, who was also not a signatory, said in a written statement the debate instead comes down to a difference between two things.

Firstly, the spread of disease via respiratory droplets which are released when an infectious person coughs or sneezes which are relatively heavy and therefore don't travel very far. The WHO and other official bodies assume this to be the main way SARS-CoV-2 is spread. Others argue what they describe as airborne transmission—where smaller particles are suspended in the air, may travel longer distances but are more likely to dry out—also play a role in the virus being passed on.

Vazquez-Boland said: "For the public it may be difficult to differentiate between the different situations and technical definitions."

Lisa Brosseau, a research consultant at the University of Minnesota Center for Infectious Disease Research and Policy and retired professor at the University of Illinois at Chicago, told Newsweek via email the WHO believes only droplet transmission is involved "which is [the] propulsion of large droplets in the face and mucous membranes—and not inhalation."

Tang said he believes the WHO are using an outdated definition of airborne by applying the term to droplet sizes of less than 5 microns in diameter to apply to larger particles.

Aerosol transmission shouldn't be defined by size of the droplet or the distance over which it can travel, he said, but rather the focus should be on how the virus survives in different scenarios and ventilation levels.

Brosseau said: "I think they're [the signatories] feeling frustrated, because so many healthcare workers, other workers and the public are being told it's only droplet transmission and that a face covering is going to stop all the droplets, when that isn't the primary mode of transmission. I'm feeling their same frustration. It's preventing us from making good recommendations for protecting workers and the public."

She went on: "We need to focus on better ventilation, limiting the number of people indoors, increasing proximity and decreasing the amount of time people spend in contact with each other."

Regarding the widely held belief that people should stay 6 feet apart to prevent the spread of SARS-CoV-2, Brosseau said: "The 2 meters [6 feet] is not based on any real science. It's a rule of thumb based on very old data. Coughs and sneezes travel well beyond 2 meters. So do small particles, particularly if they're carried by air currents."

Brosseau said: "Distancing depends on the situation—airflow, number of people, length of time, etc. indoors. Outdoors it's a good idea to stay apart from people whose infection status you don't know, but again, there is nothing magic about 2 meters.

She concluded: "I hope that we'll start to make better, more informed decisions about risk based on science and data, not guesswork and magical thinking."