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Scientific evidence on airborne SARS-CoV-2 virus transmission from different researchers points in the same direction: Infectious aerosols are the main means of person-to-person transmission, according to experts.
It’s not that it’s without controversy.
The transmission of aerosols in favor of science “is clear, but not accepted in many circles,” said Dr. Trisha Greenhalgh. Medscape Medical News.
“In particular, some evidence-based movement professionals and some infectious disease clinics are very resistant to evidence,” added Greenhalgh, a professor of primary care health sciences at Oxford University, Oxford. , United Kingdom.
“It’s very hard to see why, because all the evidence is stacked,” Greenhalgh said.
“Scientific evidence on the spread of near-field and far-field aerosols has been clear since the beginning of the pandemic, but there was resistance to recognizing it in some circles, including medical journals,” Joseph G. Allen, DSc, MPH, he said Medscape Medical News when asked to comment.
“This is the week that the dam exploded. Three new comments came out … in the best medical journals … BMJ, The Lancet, JAMA – Pointing out that aerosols are the dominant mode of transmission, ”added Allen, an associate professor of exposure assessment science at Harvard TH Chan School of Public Health in Boston, Massachusetts.
Greenhalgh and colleagues point to an increase in COVID-19 cases following events called “super-diffusers,” the spread of SARS-CoV-2 to people through different hotel rooms, and relatively lower transmission detected. after outdoor events.
10 main reasons
Ten scientific reasons outlining air transmission were outlined in a comment posted online on April 15 in The Lancet:
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The mastery of airborne transmission rests on the long-range transmission observed in super-scattering events.
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Long-range transmissions have been reported between rooms in COVID-19 quarantine hotels, environments where infected people never spent time in the same room.
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It is estimated that among asymptomatic individuals, 33% to 59% of SARS-CoV-2 transmission is estimated and the virus could be spread through speech, producing thousands of aerosol particles and a few large drops.
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Transmission outdoors and in well-ventilated indoor spaces is lower than in enclosed spaces.
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Nosocomial infections are reported in healthcare settings where protective measures are faced with large drops, but not aerosols.
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Viable SARS-CoV-2 has been detected in the air of hospital rooms and in the car of an infected person.
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The researchers found SARS-CoV-2 in hospital air filters and construction ducts.
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They are not just humans: infected animals can infect animals in other connected cages only through an air duct.
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No strong evidence refutes the airborne transmission and the tracing of contacts allows secondary transmission in crowded and poorly ventilated interior spaces.
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Only limited evidence supports other means of transmission of SARS-CoV-2, including through fomites or large droplets.
“We thought we would summarize [the evidence] to clarify the arguments for and against. We looked for evidence against it, but found none, “Greenhalgh said.
“While other routes may contribute, we believe the air route is likely to be dominant,” the authors note.
Evidence on airborne transmission was there very early on, but the Centers for Disease Control and Prevention, the World Health Organization (WHO) and others, repeated the message that the main concern was drops and fomites.
Response to a review
The top 10 list is also a partial refutation of a systematic review funded by the WHO and published last month that points to inconclusive air transmission tests. The researchers involved in this review state that “the lack of recoverable viral culture samples of SARS-CoV-2 precludes firm conclusions about airborne transmission.”
However, Greenhalgh and colleagues point out that “this conclusion and the widespread dissemination of the findings of the review are of concern for the public health implications.”
Current authors also argue that there is already sufficient evidence on airborne transmission. “Policy should change. We don’t need more research on this issue; we need different policies,” Greenhalgh said. “We need front and center ventilation, air filtration when needed and more appropriate masks to wear indoors.”
Allen agreed that guidance has not always been at the same pace as science. “With all the new evidence accumulated on air transmission since last winter, there is still a great deal of confusion in the public about transmission modes,” he said. Allen is also curator of The Lancet COVID-19 and chairs the committee’s working group on safe work, safe schools and safe travel.
“It was only last week that the CDC backed down on ‘deep cleaning’ and rightly said the risk of touching surfaces is low,” he added. “Science has been clear about this for over a year, but the official guide has only recently been updated.”
As a result, many companies and organizations continued to focus on “hygiene theater,” Allen said, “wasting resources on cleaning surfaces. It’s amazing that many schools still close for an entire day each week to clean up.” the deep ones and some books in the library are still in quarantine. the message that shared air is the problem, not shared surfaces, is a message that still needs to be reinforced. “
The National Institute for Health Research, Economic and Social Research Council and Wellcome support Greenhalgh’s research. Greenhalgh and Allen had no relevant financial relationships to disclose.
Damian McNamara is a staff Miami-based journalist. It covers a wide range of medical specialties, including infectious diseases, gastroenterology, and critical care. Follow Damian on Twitter: @MedReporter.
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