Canada has quietly revised guidelines on how COVID-19 spread to incorporate the risk of aerosol transmission, weeks after other countries and international health organizations recognize the aerial threat of coronavirus.
Public Health Agency of Canada (PHAC) updated guidance without notice this week, and mention the risk of transmission from an aerosol – or microscopic airborne particles – for the first time.
“SARS-CoV-2, the virus that causes COVID-19, spread from an infected person to another person through respiratory droplets and aerosols created when an infected person coughs, sneezes, sings, shouts, or speak,” said the updated guidance.
“Drops vary in size from large droplets that fall to the ground quickly (within seconds or minutes) near an infected person, for small droplets, sometimes called aerosols, that linger in the air under certain conditions.”
guidelines for federal agencies earlier said the virus spreads only through inhalation of respiratory droplets, touching contaminated surfaces, and general greetings such as handshakes and hugs.
PHAC did not immediately respond to requests for comment on the CBC guidelines change.
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Guidelines change ‘which is quite large, “said aerosol experts
“This is huge,” said Linsey Marr, one of the world’s top scientists and experts aerosol in airborne transmission of virus at Virginia Tech. “The big difference now is that ventilation is important – keep is not enough.”
CBC News last month to press federal agents why they did not mention the risk of aerosol although other international institutions to do so.
The US Centers for Disease Control and Prevention (CDC) updated guidance in early October to incorporate that COVID-19 can sometimes be spread by airborne transmission, after posting erroneous and then delete the draft version of the guidelines by the end of September.
The World Health Organization has also come under fire in July after 239 scientists from 32 countries wrote an open letter calling for the UN to update the message on the risk of airborne transmission of the coronavirus.
WHO has changed the guidelines the day after the letter and acknowledged the possibility that aerosols can cause an outbreak of COVID-19 in places such as choir practice, restaurant, and fitness classes.
Update advice comes after a new mask
Update PHAC guidelines come after Canada’s Chief Public Health Officer Dr. Theresa Tam recommends the use of three-layer non-medical masks to prevent the spread of COVID Tuesday 19th ahead of winter weather can bring more people together in the room.
“This is an additional recommendation just to add another layer of protection. Science mask has really accelerated over the specific pandemic. So we just learn more as we go,” he said Tuesday.
“I think it’s because it’s winter because we are all going in, we learn more about droplets and aerosols.”
Marr said that the PHAC guidance updated in three layers of non-medical masks in line with the threat of aerosol transmission.
“If we are only concerned about the large droplets, it is pretty much almost every part of a single layer of fabric will work,” he said.
“But because we are concerned about aerosols, then we do need to think about the quality and fit our masks and we know that it has several layers of filtering masks improve performance.”
Tam said public health officials Tuesday also wants to emphasize that people should wear a mask in the room if it is not with the people in their household, another significant update to its guidance.
“It will help prevent droplets or aerosols more than if you rely solely on the distance of two meters,” he said. “Once again, add another layer.”
PHAC previously told CBC News in a statement on the 24th that it does not update the guidelines on the air transmission of September – although it said there “has been a situation in which aerosol transmission has occurred in a closed setting.”
The agency said at the time of his guidance will remain the same: limit the time spent in enclosed spaces, crowded places, and close contact situations, while maintaining the physical distancing, hand washing and mask-wearing.
Addressing aerosol transmission requires many measures
“Distancing helps, masks help, ventilation helps — no one of these things is perfect,” Marr said.
aerosol transmission, he said, will not be addressed by focusing on just one of these steps alone. “But when we combine all these things, we have not seen any outbreaks.”
PHAC also said in September that it was reviewing the evidence on the topic and acknowledge that aerosols can be suspended in the air and infect others nearby, but it was not known at the level of what happens and under what conditions.
“It is important for public health agencies to recognize this so that people can now take appropriate steps to reduce transmission,” said Marr. “And there are many organizations such as schools and businesses look to public health agencies for guidance.”
He said PHAC updated guidelines will make it more difficult for these types of organizations to ignore the threat of aerosol transmission.
Study superspreading events, such as choir practice in the state of Washington, the call center in South Korea, and a restaurant in China, has supported the conclusion that some level of transmission occurs via aerosols.
virus particles were also found in the air at a nursing home outbreak in May in Montreal, where the ventilation system is wrong can be a source of transmission of the infected 226 residents and 148 employees.
The outbreak in a spinning studio in Hamilton, Ont., Saw at least 85 people were infected and prompted the city to announce new, improved guidelines for the gym and fitness center including mandatory masking.
“The gym followed all of the guidelines: they have alienated, their cleanliness, they have people wearing masks before and after,” Marr said, “but if it was just all a big drop, then distancing and cleanliness would be enough – but obviously, it was not. ”
“Because aerosol plays an important role in the transmission and if you are only a short distance and just do hygiene, it is not enough.”
