The World Health Organization released new guidelines on the transmission of the novel coronavirus. These guidelines acknowledge some reports of airborne transmission of the virus that causes COVID-19. Though it didn’t confirm that the virus spreads through the air.

WHO acknowledged that some outbreak reports about indoor crowded spaces indicate that there is a possibility of aerosol transmission and some examples can be during choir practice, in fitness classes or in restaurants.

Though WHO said more research is needed urgently to investigate such instances and assess their significance in the transmission of COVID-19.

After reviewing the evidence, the WHO said the coronavirus that causes COVID-19 spreads through contact with contaminated surfaces or close contact with infected people spreading virus through respiratory secretion, saliva, or droplets released when a person who is infected sneezes, coughs, sings or speaks.

The new guidelines state that people should avoid crowding in places, should have good ventilation in buildings, follow social distancing and should wear a mask when physical distancing is not possible.

Jose Jimenez, a chemist at the University of Colorado said that this is a right move but a small one. It is gradually becoming clear that the pandemic is driven by super-spreading events, and that the best explanation for many events is aerosol transmission.

Linsey Marr, an aerosol expert said that WHO is using an outdated definition of droplets and aerosols. It is too focused on the size of the droplets and the distance they travel.

WHO defines aerosols as being under 5 microns since only particles that small could float in the air long enough to be inhaled.

But Jimenez and Marr mentioned that a much larger range of particle size has been shown to contribute to infection.

Instead of the size, they believe the differences between droplets and aerosols should be based on how the infection occurs.

When a person inhales the virus and gets infected, its an aerosol and when the infection occurs by contact, they are droplets.

But WHO has focused on airborne transmission at long distances and Marr notes that breathing in aerosols is more worrisome when in close contact and when people are in the same room.