Public Health Canada did not previously mention aerosol-based transmission in federal recommendations.
Canada has silently revised its guidelines on how COVID-19 is spread to include the risk of transmission by aerosol particles, weeks after other countries and international health organizations acknowledged the airborne threats of the coronavirus.
Public Health Canada (PHAC) updated the guidelines, which did not announce this week, addressing the risk of transmission from aerosols – or microscopic airborne particles for the first time.
“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.”
Previously the federal agency’s guidelines said the virus was spread only by breathing respiratory droplets, touching contaminated surfaces and casual greetings such as shaking hands and hugging.
“This is pretty major,” said Linsey Marr, one of the top aerosol scientists in the world and an expert on the airborne transmission of viruses at Virginia Tech. “The big difference now is that ventilation is important — distancing alone is not enough.”
The World Health Organization was also criticized in July after 239 scientists from 32 countries wrote an open letter urging the UN agency to update its message on the coronavirus’s risk of airborne transmission.
The WHO revised its guidelines a few days after the letter and acknowledged the possibility that aerosols could lead to COVID-19 outbreaks in places like choir practice, restaurants, and fitness classes.
Updates to new guidelines from Public Health Canada-PHAC come after Canada’s Public Health Director, Dr. Theresa Tam, recommended a non-medical three-layer mask on Tuesday. to prevent the spread of COVID-19 before winter weather could bring more people together indoors.
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