239 scientists say COVID-19 is airborne

Scientists from around the world are pushing for recognition that it is possible COVID-19 can spread through airborne transmission.

In an open letter, 239 experts from a range of science and engineering fields, including virology, aerosol physics and medicine, appealed to international health authorities to recognise the potential for airborne spread of the virus.

Air quality expert and QUT Professor Lidia Morawska, who is leading the charge, said the appeal is to address the overwhelming research finding that an infected person exhales airborne virus droplets when breathing and talking that can travel further than the current 1.5-metre social distance requirement.

The World Health Organization and the US Centers for Disease Control and Prevention maintain that people have to worry about only two types of transmission: inhaling respiratory droplets from an infected person in their immediate vicinity or, less common, touching a contaminated surface and then their eyes, nose or mouth.

Morawska said studies by signatories and other scientists have shown “beyond any reasonable doubt” that viruses are exhaled in microdroplets small enough to remain aloft in the air.

WHO officials have acknowledged that the virus can be transmitted through aerosols but say that occurs only during medical procedures such as intubation that can spew large quantities of the microscopic particles.

Dr Benedetta Allegranzi, a top WHO expert on infection prevention and control, said in response to questions from the Los Angeles Times that Morawska and her group presented theories based on laboratory experiments rather than evidence from the field.

"We value and respect their opinions and contributions to this debate," Allegranzi wrote in an email. But in weekly teleconferences, a large majority of a group of more than 30 international experts advising the WHO has "not judged the existing evidence sufficiently convincing to consider airborne transmission as having an important role in COVID-19 spread".

She added that such transmission "would have resulted in many more cases and even more rapid spread of the virus".

In their letter the 239 signatories addressed that issue, writing: “The evidence is admittedly incomplete for all the steps in COVID-19 microdroplet transmission, but it is similarly incomplete for the large droplet and fomite modes of transmission.

“Following the precautionary principle, we must address every potentially important pathway to slow the spread of COVID-19.”

As such, Morawska said to curb its spread, communities would need to: ensure for sufficient ventilation, particularly in public buildings, workplaces, schools, hospitals, and aged care homes; supplement general ventilation with airborne infection controls such as local exhaust, high efficiency air filtration, and germicidal ultraviolet lights; and avoid overcrowding.

She added simple steps like opening both doors and windows can dramatically boost air flow rates in many buildings.

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