New WHO guidance calls for more evidence on airborne transmission

The World Health Organization on Thursday released new guidelines on the transmission of the novel coronavirus that acknowledge some reports of airborne transmission of the virus that causes Covid-19, but stopped short of confirming that the virus spreads through the air.

In its latest transmission guidance, issued on Thursday, the WHO acknowledged that some outbreak reports related to indoor crowded spaces have suggested the possibility of aerosol transmission, such as during choir practice, in restaurants or in fitness classes.

How frequently the coronavirus can spread by the airborne or aerosol route - as opposed to by larger droplets in coughs and sneezes - is not clear.

But the WHO said more research is “urgently needed to investigate such instances and assess their significance for transmission of Covid-19.”

Based on its review of the current evidence, the WHO said the novel coronavirus that causes Covid-19 spreads between people through direct or indirect contact with contaminated surfaces or close contact with infected people who spread the virus through saliva, respiratory secretions or droplets released when an infected person coughs, sneezes, speaks or sings.

The report follows an open letter from scientists who specialize in the spread of disease in the air - so-called aerobiologists - that urged the global body to update its guidance on how the respiratory disease spreads to include aerosol transmission.

Only a very small number of diseases are believed to be spread via tiny floating particles or aerosols. These include measles and tuberculosis - two highly contagious diseases that require extreme precautions to prevent exposure.

WHO guidance acknowledges that airborne transmission of the novel coronavirus can occur during specific medical procedures that generate aerosols, such as when performing intubation.

In these circumstances, they advise medical workers performing such procedures to wear heavy duty N95 respiratory masks and other protective equipment in an adequately ventilated room.

Any change in the WHO’s assessment of risk of transmission could affect its current advice on keeping 1-meter (3.3 ft)physical distancing. Governments, which also rely on the agency for guidance, may also have to adjust public health measures aimed at curbing the spread of the virus.