Hundreds of scientists say there is evidence that novel coronavirus can linger in smaller particles in the air and infect people indoors, which could mean that masks may be required while inside.
The new findings have prompted researchers to call for the World Health Organization to revise recommendations that could radically affect how people go about their days while indoors in confined spaces.
If their conclusion is accurate, people may need to keep wearing masks indoors, even when they are socially distanced.
Another possibility is that ultraviolet light would be deployed to kill tiny, infected particles.
The WHO has said the coronavirus disease spreads primarily from person to person through small droplets from the nose or mouth, which are expelled when a person with COVID-19 coughs, sneezes or speaks.
In an open letter to the agency, which the researchers plan to publish in a scientific journal next week, 239 scientists in 32 countries outlined the evidence showing smaller particles can infect people.