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Aerosol spread of coronavirus underscores importance of avoiding ‘three Cs’: Tam

For the first time, Canadian health officials are officially recognizing that COVID-19 can spread through tiny droplets known as aerosols that can linger in the air, but their advice for staying safe is not dramatically different.

Dr. Theresa Tam, Canada’s chief public health officer, said at a press conference Friday that the potential for aerosol transmission highlights the importance of wearing a mask and avoiding the three Cs — closed spaces, crowded spaces and close contact.

“There is recognition that droplets of different sizes will play a role, how much or how important a role is played by the smaller-sized droplets, or the aerosols, still remains an area of research,” she said.

The Public Health Agency of Canada amended its guidance on how the virus spreads on Tuesday, acknowledging a month after the U.S. CDC that minuscule, airborne particles can play a role in the transmission of the virus.

“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,” Tam said at a press conference Tuesday.

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“The droplets vary in size from large droplets that fall to the ground rapidly within seconds or minutes near the infected person to small droplets, sometimes called aerosols, which linger in the air under some circumstances.”

Tam said Friday that she and her deputy, Dr. Howard Njoo, have been discussing the potential for aerosol transmission for months prior to the official change, and the “three Cs” guidance issued last summer reflects the epidemiological evidence on so-called superspreader events.

With the winter approaching — making it harder to go outside or open a window — Tam said it was important to look at other guidance to protect Canadians from the virus.

PHAC has issued new recommendations on ventilation, since good airflow can diminish the possibility that aerosols could linger in the air and be inhaled.

A spokesperson for the agency said new evidence and research is being reviewed continually as part of their response to the coronavirus pandemic.


“We are committed to continuing to keep Canadians informed of the latest available scientific evidence and expert opinion, so they can make informed decisions to keep themselves and their family safe and healthy,” PHAC spokesperson Anna Maddison said in a statement.

The agency also recommended Tuesday that Canadians also put a third layer in their masks in order to beef up their protection from the virus.

More than 253,000 Canadians have tested positive for the virus that causes COVID-19 as of Friday, including 10,400 who have succumbed to the illness.

—With a file from Saba Aziz, Global News

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