Alberta doctor joins hundreds of scientists saying coronavirus is airborne

An Alberta physician is one of 239 scientists in 32 countries who signed an open letter calling on the World Health Organization to recognize airborne transmission as a possibility with the coronavirus.

The letter published Monday in the academic journal Clinical Infectious Diseases says there is evidence that the novel coronavirus in smaller particles in the air can infect people and calls for the WHO to revise its recommendations.

The letter, titled "It is Time to Address Airborne Transmission of COVID-19", recommends measures such as improving ventilation and air filtration as well as avoiding overcrowding.

"Handwashing and social distancing are appropriate, but in our view, insufficient to provide protection from virus-carrying respiratory microdroplets released into the air by infected people," says the letter. 

"Following the precautionary principle, we must address every potentially important pathway to slow the spread of COVID-19."

It is widely accepted that the virus that causes COVID-19 spreads through large droplets — when someone coughs or sneezes, for example.

But Dr. Nelson Lee, an infectious disease expert at the University of Alberta, says he signed the letter to raise awareness that there is a whole spectrum of transmission. 

He says it's important for the scientific community and policy makers to realize that microdroplets could also be spreading the virus.

'Hang in the air'

"These particles can hang in the air for a longer period of time and travel longer than two metres," he said. 

Lee says crowded indoor environments and places with poor ventilation pose a higher risk for this kind of transmission.

"This route of transmission is not entirely accepted and often not acknowledged in public health recommendations."

However, Lee notes that long-range airborne transmission, as happens with diseases like measles, is very rare.

University of Calgary infectious disease expert Dr. Craig Jenne says large droplets do still appear to be the dominant form of transmission.

"[But] it does explain, perhaps, under the right circumstances, that air movement might be a critical piece of the puzzle. So we will have to consider that when we look at things such as schools and apartment buildings that have different types of air circulation."

Alberta Health says it's watching all emerging evidence closely in concert with Ottawa and will take additional action as required.