Canada updates COVID-19 guidance to include risk of aerosol transmission

By Levon Sevunts
In a major departure from its previous advice, the Public Health Agency of Canada (PHAC) now says that the coronavirus can also be transmitted through tiny aerosol particles that could linger in the air, especially in enclosed spaces with poor ventilation.
The agency quietly updated its virus transmission guidance earlier on Tuesday, bringing them in line with the advice of the World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC).
“SARS-CoV-2, the virus that causes COVID-19, spreads from an infected person to others through respiratory droplets and aerosols created when an infected person coughs, sneezes, sings, shouts, or talks,” the updated guidance said.
“The droplets vary in size from large droplets that fall to the ground rapidly (within seconds or minutes) near the infected person, to smaller droplets, sometimes called aerosols, which linger in the air under some circumstances.”
However, the relative infectiousness of droplets of different sizes is not clear, PHAC noted.
“Infectious droplets or aerosols may come into direct contact with the mucous membranes of another person’s nose, mouth or eyes, or they may be inhaled into their nose, mouth, airways and lungs,” the updated guidance said.
“The virus may also spread when a person touches another person (i.e., a handshake) or a surface or an object (also referred to as a fomite) that has the virus on it, and then touches their mouth, nose or eyes with unwashed hands.”
The federal agency’s guidelines previously said the virus spreads only through breathing in respiratory droplets, touching contaminated surfaces and common greetings like handshakes and hugs.
The change comes as Canada’s Chief Public Health Officer, Dr. Theresa Tam, urged Canadians to use three-layer masks to slow the spread of the coronavirus.
She also called on Canadians to “try to avoid the three Cs – close spaces with ventilation, crowded places with large numbers of people gathered and close contact situations where you can’t maintain physical distancing.”
Speaking at a press conference with Prime Minister Justin Trudeau on Tuesday, Tam said the science around the coronavirus transmission is constantly evolving, adding that Canadians need to be “flexible and adapting to new challenges.”
The WHO amended its guidelines in early July after coming under fire from more than 230 scientists who urged the UN health agency to update its advice on the possible aerosol transmission of the virus.
The CDC followed suit in early October.
With files from CBC News