Despite WHO and CDC guidance, Canada still downplays the risk of coronavirus spread in the air

As researchers around the world compete to learn as much as possible about the new coronavirus, many health agencies have the potential to transmit it via aerosols, or microscopic airborne particles. I conclude, but Canada has not followed that lead so far.

Initially, the new coronavirus was thought to spread only through large droplets. It was recommended that the droplets fall to the ground within a distance of 2 meters and settle, maintain a social distance, and be 2 meters away from other droplets. However, the understanding of viruses is evolving, and it is widely believed that they can spread from small droplets containing virus particles and can remain suspended in the air for extended periods of time.

World Health Organization fired in July after 239 scientists from 32 countries Wrote an open letter Request UN agencies to update their message on the risk of aerial transmission of the coronavirus.

WHO revised guidelines A few days after the letter, I acknowledged that these small droplets, also known as aerosols, could lead to the development of COVID-19 in the following locations: Chorus practice, Restaurant And Fitness class..

Centers for Disease Control and Prevention (CDC) Updated guidelines On Monday, COVID-19 says it can then spread due to airborne infections. Post by mistake and delete later Draft version of the guidelines.

“I’m happy and relieved because they recognize the best science we have,” said Lindsay Marr, an expert on aerosol virus infections at Virginia Tech.

“You can’t bend a curve unless you pay attention to this transmission route.”

There are no plans to update the guidelines in Canada

Still Public Health Agency of Canada Guidelines It does not mention the transmission of aerosols, instead saying that the virus inhales respiratory droplets, touches contaminated surfaces, and spreads only by common greetings such as handshakes and hugs.

In addition to WHO and CDC Germany And Italy Recognize aerosols as a risk. However, PHAC told CBC News that it had not updated its guidance on airborne propagation, despite admitting that aerosol diffusion had occurred.

“Aerosol infections of COVID-19 in ventilated and unventilated environments are still being studied,” a federal statement said. “There was a situation where aerosol propagation occurred in a closed environment.”

The PHAC states that the guidance remains the same. Limit time spent in closed spaces, crowded areas, and in close contact situations where “no controls, protocols, or policies have been implemented to reduce the risk of COVID-19, such as good ventilation.” PHAC also recommends maintaining physical distance, hand washing, and wearing a mask.

However, Dr. Raymond Terrier, an infectious disease expert, medical microbiologist, and assistant professor at McGill University in Montreal, acknowledged that ventilation plays a role in controlling COVID-19 infection. He states that he acknowledges that aerosols are an important pathway. Of transmission.

This is because ventilation does not change the risk of infection due to larger respiratory droplets or contact with contaminated surfaces.

“When promoting the avoidance of poorly ventilated indoor areas, ventilation only affects aerosol propagation, so we implicitly admit to accepting aerosol propagation,” he said.

“So, if you’re driving ventilation, what are you talking about, if not aerosols?”

Authorities are also reviewing evidence on this topic, admitting that aerosols can float in the air and infect others nearby, but under the rate and conditions under which they occur, ” Unknown. “

“Resistance is very strong in Canada,” says Tellier.

“There is a lot of data that builds a very strong case where aerosol infections are also part of the disease transmission.”

Research Superspreader event, Such Chorus practice In Washington Call center With Korea Restaurant China supports the conclusion that some propagation is occurring in the air.

See | Lindsay Marr on evidence that the virus can levitate

The signatories of the letter urging WHO to change its recommendations on airborne infections with COVID-19 say it is wise to do everything possible to delay the virus. 6:00

Terrier is reluctant to allow aerosol transmission due to the need for broader personal protective equipment such as N95 masks in hospitals, and ventilation and air circulation in public buildings that can be expensive. He said it could be related to the increase in the number of people.

“I’ve heard anecdotes about the school district, where I pointed out the old CDC guidance and said,” Well, they don’t say anything about it, so we don’t have to do anything about it. ” Said Ma. “Even when people were urging them to pay attention to ventilation.”

The importance of masks

Jose Jimenez, a professor of chemistry at the University of Colorado, who specializes in aerosol science, said the easier way to see aerosols is to compare them to smoke that is exposed to higher levels of exhaled smoke as they approach infected individuals. I did. , Emphasizes the importance of wearing a tight fit mask.

“If anyone in the world could spend 10 minutes paying attention to the tightness of the mask, that would be a huge benefit,” he said. “Given how bad most masks are worn, it’s almost surprising that masks are effective.”

Dr. Mark Loeb, an infectious disease expert at McMaster University School of Medicine in Hamilton, believes that most COVID-19 infections occur over short distances, but that there are situations in which long-range infections can occur. Stated.

One example he pointed out Outbreak of Nursing Home in Montreal Viral particles were found in the air, and a defect in the ventilation system could have been the source of infection, affecting 226 residents and 148 employees.

“So I think I have to say that in certain situations it can happen,” Loeb said. “But I think there are sometimes over-interpretations.”

He said that when experts from different schools see the same outbreak, they can reach completely different conclusions.

For example, consider a study of a choir of 61 members on March 10 in Mount Vernon, Washington for a two and a half hour practice session.

They sat close to each other, sang together, shared snacks, and piled up chairs when it was over.

Two weeks later, 53 of the attending members confirmed or estimated cases of COVID-19. Three of those people were hospitalized. Two people died.

“Some say this is the definitive proof of aerosolization. If you look more closely, you’ll say that people are in close contact and walking around,” he said.

“It can be impossible to say that it is definitely one or the other.”

Regardless of the role of aerosol infection in the spread of COVID-19, Terrier said the burden of proof was much higher for some reason.

“There is a very high threshold for the scientific certainty of aerosols,” he said. “For some reason, surface-based transmission was accepted with much less evidence.”

WHO has “no specific reports” of COVID-19 directly from contact with contaminated surfaces, despite studies consistently showing that the virus can survive for hours or days7. Said on the moon.

“No one has been infected by touching the package,” Loeb said.

As part of that, the CDC says the virus spreads “Not very common” PHAC claims it is one of the viral methods because it touches contaminated surfaces. “Most commonly spread.”

“In my view, there are many unknowns and we need to be open,” he added. “We have to see all the data.”

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