New Delhi: Days after researchers claimed that the novel Coronavirus is 'airborne', the World Health Organisation acknowledged some reports of transmission of the virus but also emphasized that more evidence in terms of research was required to say that the virus is in the air.

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

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

The brief maintained that "the coronavirus that causes COVID-19 spreads through 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."

Virus spread can be through asymptomatic people

The WHO also asserted that the virus may be spread by people who do not have symptoms: “Infected people can transmit the virus both when they have symptoms and when they don’t have symptoms,” the agency said.

The report comes in the wake of an open letter written by over 200 scientists urging the global body to update its guidelines on how the respiratory disease spreads to include aerosol transmission.

"This is a move in the right direction, albeit a small one. It is becoming clear that the pandemic is driven by super-spreading events, and that the best explanation for many of those events is an aerosol transmission," said Jose Jimenez, a chemist at the University of Colorado who signed the letter, which was published on Monday in the journal Clinical Infectious Diseases was quoted as saying by Reuters.

Only a very small number of diseases are believed to be spread via aerosols, or tiny floating particles. 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.