Health
Coronavirus: Canadian experts say not to get hung up on term ‘airborne’ transmission – Globalnews.ca
A group of 239 scientists and physicians urging the World Health Organization to recognize the potential for airborne transmission of the novel coronavirus have sparked debate over how COVID-19 is spreading.
But some Canadian infectious disease experts say not to get hung up on the term “airborne,” and that the safety precautions we’re already taking to slow the spread of the virus are working.
“To the general public the word (airborne) can be pretty confusing because it suggests that COVID is gonna come through the keyhole and get you in your sleep. And well, it isn’t,” said Colin Furness, an epidemiologist with the University of Toronto.
“No one is suggesting COVID behaves anything like measles… That’s not the point (the scientists) are trying to make.”
In an open letter to the WHO published Monday, scientists across 32 countries called for the organization to revise its safety recommendations to mitigate possible spread of COVID-19 through aerosols — tiny, light particles expelled when people cough, sneeze or breathe that stay suspended in the air for longer periods of time.
The WHO currently classifies SARS-CoV-2 as a droplet virus, spreading through larger, heavier particles that can travel one to two metres before hitting the ground. While the organization acknowledged in a press briefing Tuesday that there is “some evidence emerging” for aerosol spread, they also say it is “not definitive.”
Furness says from what we’ve seen of COVID spread in clinical practice, it’s droplet based, but the scientists behind the letter have a point, too.
He said people release particles of all sizes when they breathe, and SARS-CoV-2 can be found in smaller droplets. But that doesn’t mean they are effective in trasmitting the virus, he added.
The scientists’ letter mentions a COVID-19 outbreak at a Chinese restaurant where customers at tables further than two metres apart became infected. While the authors use that as an argument for COVID’s spread through aerosols, Furness said that’s not necessarily the case.
“It could be (evidence of aerosol spread) but it also could be that they touched the same thing. We don’t know,” he said. “Also one would need to explain why didn’t everyone in the restaurant get sick?”
“So WHO is right that there isn’t a clear case. And the scientists who signed that letter are right saying we do need to look at this … because it could have an impact on what we say is safe.”
Dr. Bonnie Henry, B.C.’s provincial health officer, praised WHO on Monday for “doing an amazing job trying to keep up with what’s going on,” and said she thought the scientists’ letter was “trying to foment a bit of controversy.”
Henry added that while COVID does seem to be released in small droplets as well as large droplets, we don’t know how potent those smaller particles are.
“Where there’s some challenges is how much is due to the small aerosols which are transmitted when I’m close to you, or the larger droplets that tend to fall out more readily,” Henry said. “So it’s really a bit of nuance, I think.”
Dr. Zain Chagla, an infectious disease physician and an associate professor at McMaster University in Hamilton, doesn’t believe the novel coronavirus is transmitting through aerosols, at least not to an extent we should be worried about.
If it was “we’d be in trouble,” he said.
“We would have seen huge rates of transmission if this was a predominantly aerosol virus. We would have not been able to control it as well as we did.
“In reality, there is probably some degree of small aerosols that would carry COVID-19 in average day-to-day contact, but it’s probably very minimal.”
Chagla also believes the argument for aerosol versus droplet transmission is “more of a discrepancy on the exact scientific terminology” of what airborne actually means.
COVID-19 does have the potential to transmit through small particles when patients in hospital are undergoing “aerosol-generating procedures” like being intubated, Chagla said, and WHO also acknowledges that.
In those instances, health-care workers are given proper personal protective equipment (PPE), including N95 masks, which protect against small airborne particles.
But Chagla highlighted a specific case from early in the pandemic, before evidence of community spread, when health-care workers treated a COVID patient in California without proper PPE. Out of 121 health-care workers that treated the patient and performed “multiple aerosol-generating procedures,” only three got sick.
“So you had 118 individuals that … did not wear N95 masks which would be the only protection against aerosol viruses, and they did not get infected,” he said.
Chagla compared the situation to measles, which has a reproduction number of about 18 –meaning one infected person will infect 18 others. Measles particles can stay suspended in the air of a room for hours after an infected person leaves it, Chagla said, and you can catch the virus from a much further distance away.
Dr. Howard Njoo, Canada’s deputy chief public health officer, said Wednesday that evidence so far has not shown COVID to be airborne “in that classic definition in a sense as measles.”
“And certainly based on what we’ve done so far in terms of public health measures, they’ve been proven effective,” he added.
Furness said COVID-19 has a reproduction number of two, while Njoo believes that number to be in the “3, 4 or 5” range, based on the most recent epidemiology.
Other coronaviruses have smaller reproduction numbers (0.5 for SARS and 1.5 for H1N1), so Furness says that could mean there’s more going on with COVID.
“COVID is doing something to be more infective than your average respiratory virus,” Furness said. “And I’m nowhere near saying it’s airborne, because I don’t think that’s an appropriate statement. But I think those aerosols, those smaller droplets that we’re disregarding, they might be important.”
Both Furness and Chagla say there’s no indication that the general public will need to do any more to protect from potential aerosol spread of the virus.
Chagla says the points emphasized by the scientists in the letter mirror what we’re already doing, like having events outdoors rather than indoors to ensure proper air flow.
Face coverings become more important if we have to worry about aerosols, Furness says. And even though smaller particles can get through cloth masks, the fabric will slow them down.
“The more we can slow down the trajectory of what comes out of your mouth, the less it disperses,” he said.
— With files from Hina Alam
© 2020 The Canadian Press
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Interior Health says it delivered nearly 800,000 immunization doses last year — a number almost equal to the region’s population.
The released figure of 784,980 comes during National Immunization Awareness Week, which runs April 22-30.
The health care organization, which serves a large area of around 820,000, says it’s using the occasion to boost vaccine rates even though there may be post-pandemic vaccine fatigue.
“This is a very important initiative because it ensures that communicable diseases stay away from a region,” said Dr. Silvina Mema of Interior Health.
However, not all those doses were for COVID; the tally includes childhood immunizations plus immunizations for adults.
But IHA said immunizations are down from the height of the pandemic, when COVID vaccines were rolled out, though it seems to be on par with previous pre-pandemic years.
Interior Health says it’d like to see the overall immunization rate rise.
“Certainly there are some folks who have decided a vaccine is not for them. And they have their reasons,” said Jonathan Spence, manager of communicable disease prevention and control at Interior Health.
“I think there’s a lot of people who are hesitant, but that’s just simply because they have questions.
“And that’s actually part of what we’re celebrating this week is those public health nurses, those pharmacists, who can answer questions and answer questions with really good information around immunization.”
Mima echoed that sentiment.
“We take immunization very seriously. It’s a science-based program that has saved countless lives across the world and eliminated diseases that were before a threat and now we don’t see them anymore,” she said.
“So immunization is very important.”
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The U.S. Food and Drug Administration said Tuesday that samples of pasteurized milk had tested positive for remnants of the bird flu virus that has infected dairy cows.
The agency stressed that the material is inactivated and that the findings “do not represent actual virus that may be a risk to consumers.” Officials added that they’re continuing to study the issue.
“To date, we have seen nothing that would change our assessment that the commercial milk supply is safe,” the FDA said in a statement.
The announcement comes nearly a month after an avian influenza virus that has sickened millions of wild and commercial birds in recent years was detected in dairy cows in at least eight states. The Agriculture Department says 33 herds have been affected to date.
FDA officials didn’t indicate how many samples they tested or where they were obtained. The agency has been evaluating milk during processing and from grocery stores, officials said. Results of additional tests are expected in “the next few days to weeks.”
The PCR lab test the FDA used would have detected viral genetic material even after live virus was killed by pasteurization, or heat treatment, said Lee-Ann Jaykus, an emeritus food microbiologist and virologist at North Carolina State University
“There is no evidence to date that this is infectious virus and the FDA is following up on that,” Jaykus said.
Officials with the FDA and the USDA had previously said milk from affected cattle did not enter the commercial supply. Milk from sick animals is supposed to be diverted and destroyed. Federal regulations require milk that enters interstate commerce to be pasteurized.
Because the detection of the bird flu virus known as Type A H5N1 in dairy cattle is new and the situation is evolving, no studies on the effects of pasteurization on the virus have been completed, FDA officials said. But past research shows that pasteurization is “very likely” to inactivate heat-sensitive viruses like H5N1, the agency added.
Matt Herrick, a spokesman for the International Dairy Foods Association, said that time and temperature regulations for pasteurization ensure that the commercial U.S. milk supply is safe. Remnants of the virus “have zero impact on human health,” he wrote in an email.
Scientists confirmed the H5N1 virus in dairy cows in March after weeks of reports that cows in Texas were suffering from a mysterious malady. The cows were lethargic and saw a dramatic reduction in milk production. Although the H5N1 virus is lethal to commercial poultry, most infected cattle seem to recover within two weeks, experts said.
To date, two people in U.S. have been infected with bird flu. A Texas dairy worker who was in close contact with an infected cow recently developed a mild eye infection and has recovered. In 2022, a prison inmate in a work program caught it while killing infected birds at a Colorado poultry farm. His only symptom was fatigue, and he recovered.
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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.
Canada is about where it should be when it comes to childhood vaccines, but for adult vaccinations it’s a different story.
Dr. Vivien Brown of Immunize Canada says the overall population should have rates of between 80 and 90 per cent for most vaccines, but that is not the case.
She says most children are in that range but not for adult vaccines and ultimately the most at-risk populations are not being reached.
She says the population is under immunized for conditions such as pneumonia, shingles, tetanus, and pertussis.
Brown wants people to talk with their family physician or pharmacist to see if they are up-to-date on vaccines, and to get caught up because many are “killer diseases.”
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