Is the coronavirus airborne? What we know about COVID-19 transmission

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More than 200 scientists and experts across the globe penned an open letter on Monday to public health bodies, including the World Health Organization, arguing there’s significant evidence the coronavirus can persist in the air and spread in airborne particles from person to person. The letter, published in the journal Clinical Infectious Diseases on Monday, advocates for “the use of preventative measures to mitigate this route of airborne transmission” and was signed by 239 researchers from 32 countries.

The existence of the open letter was first reported by The New York Times and Los Angeles Times on Saturday, describing the WHO as an organization “out of step with science” on the matter.

But the science isnt yet settled on whether SARS-CoV-2, the coronavirus that causes COVID-19, spreads effectively and causes disease this way. It’s not a yes or no equation, and like many aspects of the pandemic, it’s a puzzle that remains unsolved.

“It’s possible and even likely that airborne transmission occurs for SARS-CoV-2 sometimes,” Babak Javid, an infectious diseases physician at the Tsinghua University School of Medicine, said in a statement. “It’s not at all clear how common this is.”

The WHO’s official guidance on the matter is the virus moves from person to person via “small droplets” that are expelled when a person with COVID-19 coughs, sneezes or speaks. These droplets are too heavy to travel great distances, sinking quickly to the ground. In addition, it states the virus can be picked up from surfaces. That’s why hand-washing and social distancing are important to help curb the spread.

But the signatories in the open letter argue SARS-CoV-2 lingers in the air, and this may play a role in transmission. They believe when a person with COVID-19 expels virus, the particles remain aloft and can travel great distances on air currents, particularly where ventilation is poor. “It is understood that there is not as yet universal acceptance of airborne transmission of SARS-CoV2; but in our collective assessment there is more than enough supporting evidence so that the precautionary principle should apply,” they write.

To mitigate the risk of airborne transmission, they propose two major…