The World Health Organization has acknowledged evidence that coronavirus can be spread by tiny particles suspended in the air.
An official says airborne transmission can’t be ruled out in crowded, closed or poorly ventilated settings.
If the evidence is confirmed, it may affect guidelines for indoor spaces.
Up until now the WHO has said that the virus is spread in droplets when people cough and sneeze.
WHO officials have urged caution, saying the evidence discovered by scientists at the University of Colorado is preliminary and requires further assessment.
Benedetta Allegranzi, the WHO’s technical lead for infection prevention and control, said that evidence emerging of airborne transmission of the virus in “crowded, closed, poorly ventilated settings… cannot be ruled out”.
Yesterday the president of the Royal Society criticised UK policy on the use of face masks, saying the country was going against widely adopted guidance around the world.
Professor Venki Ramakrishnan said not wearing a mask should be considered an act of anti-social behaviour similar to not wearing a seatbelt.
He said: “It used to be quite normal to have quite a few drinks and drive home, and it also used to be normal to drive without seat belts.
“Today both of those would be considered anti-social, and not wearing face coverings in public should be regarded in the same way.”If all of us wear one, we protect each other and thereby ourselves, reducing transmission.”