The World Health Organization has acknowledged there is emerging evidence that the coronavirus can be spread by tiny particles suspended in the air.
The airborne transmission could not be ruled out in crowded, closed or poorly ventilated settings, an official said.
If the evidence is confirmed, it may affect guidelines for indoor spaces.
An open letter from more than 200 scientists had accused the WHO of underestimating the possibility of airborne transmission.
The WHO has so far said that the virus is transmitted through droplets when people cough or sneeze.
“We wanted them to acknowledge the evidence,” Jose Jimenez, a chemist at the University of Colorado who signed the paper, told the Reuters news agency.
“This is definitely not an attack on the WHO. It’s a scientific debate, but we felt we needed to go public because they were refusing to hear the evidence after many conversations with them,” he said.