In a forthcoming paper, 239 scientists from more than 30 countries are pushing the World Health Organization to pay more attention to the possible airborne spread of SARS-CoV-2.
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In a forthcoming paper, “It is Time to Address Airborne Transmission of COVID-19,” 239 scientists from more than 30 countries are pushing the World Health Organization (WHO) to pay more attention to the possible airborne spread of SARS-CoV-2, the novel coronavirus that causes COVID-19.
At this time, the WHO and other public health organizations’ guidelines refer to primary spread of the virus on droplets expelled when people with the disease sneeze, cough, or potentially speak loudly or sing. These are on “large respiratory droplets,” and once they are expelled, they quickly fall to the ground.
However, the researchers believe that airborne transmission via aerosolized particles, much smaller particles that can hang in the air, is more common than originally believed. They plan to submit their open letter to the WHO today and plan to publish it in a scientific journal soon after.
So far, the WHO has indicated that airborne transmission of SARS-CoV-2 is only possible after medical procedures that generate aerosols, which are droplets smaller than 5 microns. In that regard, appropriate ventilation and N95 masks are really only required in the cases of those post-medical procedures. And recent studies have suggested that there is little evidence of transmission of the virus from surfaces.
Benedetta Allegranzi, the WHO’s technical lead on infectious control, said, “Especially in the last couple of months, we have been stating several times that we consider airborne transmission as possible but certainly not supported by solid or even clear evidence. There is a strong debate on this.”
The New York Times, however, wrote, “But interviews with nearly 20 scientists—including a dozen WHO consultants and several members of the committee that crafted the guidance—and internal emails paint a picture of an organization that, despite good intentions, is out of step with science.”
However, most of those experts also expressed sympathy with the WHO’s growing “portfolio and shrinking budget” and pointed out that the organization is also balancing difficult political relationships, particularly with the U.S. and China.
The 20 scientists interviewed saved most of their criticism for the infection and control committee, which they said was too rigid and had an “overly medicalized view of scientific evidence,” and was also slow and risk-averse in changing its guidance.
“They’ll die defending their view,” one unnamed WHO consultant said.
“I do get frustrated about the issues of airflow and sizing of particles, absolutely,” said Mary-Louise McLaws, a committee member and epidemiologist at the University of New South Wales in Sydney, Australia. “If we start revisiting airflow, we would have to be prepared to change a lot of what we do. I think it’s a good idea, a very good idea, but it will cause an enormous shudder through the infection control society.”
The experts who are arguing the virus can be aerosolized point in particular to cases where airborne transmission seems to have occurred, especially in spaces with poor ventilation and crowds. They claim the WHO is making an artificial distinction between small aerosol particles and larger droplets, though people with COVID-19 can produce both.
“We’ve known since 1946 that coughing and talking generate aerosols,” said Linsey Marr, an expert in airborne transmission of viruses at Virginia Tech.
However, researchers have not been able to grow the coronavirus in the laboratory from aerosols. That doesn’t necessarily mean aerosolized SARS-CoV-2 is not infective. Most of the samples in those experiments were collected from hospital rooms that had good air flu, and they believe that was likely diluting viral levels.
There also appears to be a lot of public misconceptions about how viruses, in general, spread through the air. Measles, for examples, does seem to travel long distances through the air and is high infectious. Many other viruses are not.
People typically “think and talk about airborne transmission profoundly stupidly,” said Bill Hanage, an epidemiologist at the Harvard TH Chan School of Public Health. “We have this notion that airborne transmission means droplets hanging in the air capable of infecting you many hours later, drifting down streets, through letter boxes and finding their way into homes everywhere.”
But few if any experts believe the coronavirus acts that way. It appears to be most infectious when people are in lengthy contact at close range, especially inside. This is most notable in so-called superspreader events, which is what many of these researchers are concerned about, because the aerosol transmission appears to be what is happening in those situations.
Part of the argument goes that it is better to err on the side of caution, assume it can be aerosolized, and strongly encourage wearing masks to minimize the spread, rather than to wait for definitive proof of aerosolization, assuming definitive proof can even be determined.
The WHO, for its part, told CNBC today that it was aware of the open letter and that its experts were reviewing its contents. They expected it will be covered at the group’s press conference today and that the organization continually assess “ongoing research on the ways that COVID-19 is spread and will continue to share updated findings.”
