The letter, led by internationally recognised air quality and health expert Lidia Morawska from the Queensland University of Technology, makes an appeal for public health organisations like the WHO to address the "overwhelming" research on the dangers of microdroplets.
There is growing evidence that small droplet (airborne) transmission is a significant route of infection indoors.
"We are concerned that people may think they are fully protected by following the current recommendations, but in fact, additional airborne precautions are needed to further reduce the spread of the virus," Professor Morawska says.
Many studies conducted on the spread of MERS and influenza have also proved the risk of aerosol transmission, Professor Morawska said.
In the latest interim guidance, the WHO said current evidence suggests COVID-19 is primarily spread through large droplet transmission when people are within 1 metre of each other.