The World Health Organization acknowledged evidence emerging of the airborne spread of the novel coronavirus, after a group of scientists urged the global body to update its guidance on how the respiratory disease passes between people.
The WHO had previously said the virus that causes the COVID-19 respiratory disease spreads primarily through small droplets expelled from the nose and mouth of an infected person that quickly sink to the ground. But in an open letter published in the Clinical Infectious Diseases journal, 239 scientists in 32 countries outlined evidence that they say shows floating virus particles can infect people who breathe them in.
If the droplets particles are larger than 5-10 microns in diameter, they are referred to as respiratory droplets; if they are smaller than 5 microns in diameter, they are referred to as droplet nuclei. According to current evidence, Covid-19 virus is primarily transmitted between people through respiratory droplets and contact routes.
Because those smaller exhaled particles can linger in the air, the scientists in the group had been urging WHO to update its guidance. They are citing evidence that the virus can be present in droplet nuclei (less than 5 microns in diameter) that do travel distances longer than 1 metre, and can remain in the air for a longer time. WHO acknowledged the possibility of airborne transmission in public settings – especially in very specific conditions, crowded, closed, poorly ventilated settings that have been described.
Historically, there has been a fierce opposition in the medical profession to the notion of aerosol transmission, and the bar for proof has been set very high. A key concern has been a fear of panic. If people hear airborne, healthcare workers will refuse to go to the hospital or people will buy up all the highly protective N95 respirator masks.
Any change in the WHO’s assessment of risk of transmission could affect its current advice on keeping 1-metre (3.3 feet) of physical distance. Governments, which rely on the agency for guidance policy, may also have to adjust public health measures aimed at curbing the spread of the virus.