Many in the medical community believe that COVID-19 spreads through the air.
Some point to a paper published in the Lancet in 2021 to support their case.
It cited 10 scientific reasons in arguing that the airborne transmission is the dominant mechanism for people for contracting COVID-19.
The sixth of these 10 reasons was that the COVID-19 virus "has been detected in the air, in laboratory experiments".
Moreover, the paper cited research in peer-reviewed journals showing that the virus stayed infectious in the air for up to three hours—with a half-life of 1.1 hours.
"Viable SARS-CoV-2 [the virus causing COVID-19] was identified in air samples from rooms occupied by COVID-19 patients in the absence of aerosol generating health-care procedures and in air samples from an infected person’s car," the six researchers stated in their paper.
The lead author was Dr. Trisha Greenhalgh, professor of primary care health sciences at the University of Oxford.
"Although other studies have failed to capture viable SARS-CoV-2 in air samples, this is to be expected," Greenhalgh and the other researchers added. "Sampling of airborne virus is technically challenging for several reasons, including limited effectiveness of some sampling methods for collecting fine particles, viral dehydration during collection, viral damage due to impact forces (leading to loss of viability), reaerosolisation of virus during collection, and viral retention in the sampling equipment.
"Measles and tuberculosis, two primarily airborne diseases, have never been cultivated from room air."
Every one of these sentences was backed up with a referenced paper published in a peer-reviewed journal.
Less than three months after publication of this paper, Canadian doctors wrote an article in the Canadian Medical Association Journal about mitigating airborne transmission of COVID-19.
"Short- and long-range aerosol inhalation, or airborne transmission, of SARS-CoV-2 has been recognized by international public health agencies," they noted.
In spite of this, the chief medical health officer and vice president of public health at Vancouver Coastal Health insists there's still "great debate" over whether COVID-19 is airborne.
"Some of it's based on engineering studies trying to see how far aerosol particles may travel," Dr. Patricia Daly said in the video clip below. "That doesn't necessarily mean the virus is viable.
"What I can tell you after following up over 70,000 cases, it requires close contact to be infected with COVID-19," she continued. "So it does not spread long distances. It's not like measles, where we've had situations where a case of measles might walk through an airport, and an hour later, someone else will walk through the same airspace and come down with measles."
Some on Twitter are questioning how Daly can be so sure of this, given that many people with COVID-19 have never been tested. Yet that didn't seem to faze her.
"Since the start of this pandemic, the people who are getting infected have had close contact," Daly said. "We define it as face-to-face for 15 minutes or more, without protection, with cases. Omicron is more transmissable but transmitted in a very similar way."
That drew a derisive response from David Fisman, one of the authors of the Lancet paper and a professor of epidemiology at the University of Toronto.
Vancouver Coastal Health provides community, hospital, and long-term care services to more than one million people in Vancouver, Richmond, North Vancouver, West Vancouver, the Sea to Sky corridor, the Sunshine Coast, and mid-coast communities in B.C. It operates 13 hospitals.
B.C. Children's Hospital researchers criticize Lancet paper
In a February 5 letter to the Lancet, two researchers at B.C. Children's Hospital questioned the Greenhalgh team's argument that the dominant form of transmission is likely to be airborne.
In their letter, Dr. Alison Lopez and Dr. Jocelyn Srigley argued that the "science is far from settled". They added that "we need studies of improved quality to further understand the role of short-range and long-range aerosol transmission of SARS-CoV-2."
"First, the notion that asympto-matic or presymptomatic transmission implies an airborne mode of transmission is inaccurate, as asymptomatic and presymptomatic shedding have been described with other respiratory viruses," Lopez and Srigley wrote. "Similarly, decreased risk of transmission in an outdoor setting has been described with other viruses that are transmitted by the droplet and contact routes."
Lopez is division head of the department of pediatrics at B.C. Children's Hospital. Srigley, a medical microbiologist, is with the department of pathology and laboratory medicine at B.C. Children's Hospital.
"Second, in many reports of nosocomial infections, health-care workers used incomplete or inappropriate personal protective equipment, such as absence of eye protection, and these reports cannot rule out other modes of transmission," they continued in their letter to the Lancet. "Reports of transmission despite appropriate personal protective equipment also do not consider whether personal protective equipment was doffed appropriately. Most health-care workers make errors during doffing, which has been shown to be associated with self-contamination.
"Finally, Greenhalgh and colleagues do not account for the fact that containment measures focusing on prevention of droplet transmission have been effective at bringing the basic reproduction number below 1 in many jurisdictions."
Meanwhile, Health Minister Adrian Dix has refused an invitation to declare that COVID-19 is airborne.
This is not a mere academic debate.
Vancouver Coastal Health Authority's position underpins its insistence that portable air cleaners, such as HEPA filtration devices, are not necessary in schools.
That led one of the authors of the original Lancet paper, University of Colorado Boulder atmospheric chemist Jose-Luis Jimenez, to accuse Vancouver Coastal Health of engaging in "Flat Earth Aerosol Science".
Vancouver Coastal Health's recommendation is also opposed by Safe Schools Coalition B.C., which has given the B.C. government a failing grade in protecting students, staff, and teachers from airborne COVID-19.
A preprint paper that relied on the CERN-developed COVID Airborne Risk Assessment Tool found that two HEPA filters in a 160-square-metre classroom led to a four-fold decrease in the concentration of COVID-19 virus particles in the air.