Canada’s top doctor has been reluctant to say tiny airborne particles spread COVID-19. Under pressure, she’s reconsidering

OTTAWA—Canada’s top public health official says it may be time to revise federal guidance to provinces on how to prevent airborne infections.

Chief public health officer Dr. Theresa Tam said Tuesday the science on whether COVID-19 is transmitted via tiny aerosolized particles indoors is “evolving” and more changes to protect health-care workers, especially in long-term-care homes, could be needed.

It’s a small but controversial concession by Tam, who is under pressure from an increasingly vocal group of Canadian nurses and some infectious disease specialists — one that could lead to more stringent requirements for costly N95 respirators not only for hospitals and long-term-care homes, but also for stricter rules in public workplaces outside of health-care settings as well.

Her statement comes months after the U.S. Centers for Disease Control and the World Health Organization airborne transmission of aerosolized particles may be possible in crowded, poorly ventilated settings.

Tam’s reluctance to definitively agree that there is airborne transmission may be baffling to some, yet epidemiologist Dr. David Fisman with the University of Toronto’s Dalla Lana School of Public Health, says it is difficult for her to marshal consensus.

“Dr. Tam is having to negotiate a very challenging medical-political landscape, which makes it hard for her to simply state what many of us now take for granted,” said Fisman.

“The complexities of this situation are really closely linked to the N95 supply chain and worries that that will dry up,” he said. “And also to some very well established voices on the Canadian infection control scene who are quite adamant that this disease can’t possibly be transmitted via aerosol.”

The main way the virus is believed to be transmitted from one person to another is via larger droplets that spread when people cough, sneeze, speak, sing or shout. Those droplets are believed to fall within a two-metre distance — hence the recommendation to wear a mask, stay physically apart, frequently wash hands, and don’t touch your face.

Tam told reporters Tuesday that there is more “science and data” emerging, and she believes smaller airborne virus particles that are exhaled and can remain suspended in the air for long periods of time do “exist.” But she said “the circumstances and their importance is still being worked out.”

Even in the absence of certainty in the data, Tam said she had already recommended universal masking policies in health-care settings because of the risk to health-care workers from people who are asymptomatic or presymptomatic.

Now, she said, “given evolving opinions and evidence we will of course go back and have another look at whether certain aspects of the guidance need to be reviewed as well.”

Federal guidance to provinces already recommends droplet and contact precautions for routine care of COVID-19 patients. It requires N95 respirator masks and personal protective gear for health workers whenever aerosol-generating medical procedures are carried out, such as intubating a patient.

Canadian nurses have called on Tam and the Public Health Agency of Canada to update that federal advice to set out even more stringent rules based on the “precautionary principle” that would require employers in both acute-care and long-term-care settings to equip personnel with N95s and PPE whenever the workers come in contact with COVID-positive patients.

“The federal guidance doesn’t go far enough,” said Linda Silas, president of the Canadian Federation of Nurses, in an interview Tuesday.

Silas said even now — 10 months into the pandemic — there are hospitals in Ontario and Alberta that do not mandate the wearing of N95 respirator masks for nurses entering units where there are COVID-positive patients.

Health-care workers can make a “point of care risk assessment” and if they deem there is a risk from a patient who, say, cannot be masked and is coughing violently or vomiting, the nurse or personal support worker can ask for an N95 to be supplied.

Yet Silas said some administrators are still reluctant to dispense them as a matter of course.

The issue, she said, “is cost and fear that the supply will run out.”

Tam said Tuesday she is looking at updating recommendations on ventilation. She said modern hospitals generally already have good ventilation; meanwhile she said HVAC systems should be serviced.

And Tam said for everyone, “masking indoors when you’re not with people in your household and certainly when you can’t maintain any kind of distancing” along with “improving ventilation would be the sort of circumstance where you can reduce the impact of aerosols.”

Tam said Tuesday she is “most excited about” getting experts in ventilation together with infectious disease experts and infection control practitioners “to see if we could not find the most scientifically informed and sensible path forwards.”

Tonda MacCharles is an Ottawa-based reporter covering federal politics for the Star. Follow her on Twitter: