Written byShubham Sharma
Now, in a surprising shift in position, the UN health agency has said that airborne transmission is also a possibility in certain environments.
This comes mere days after over 200 scientists warned WHO not to undermine the case of airborne transmission.
Going by WHO's most recent COVID-19 transmission update, the novel coronavirus that causes the disease spreads mainly through respiratory droplets (usually greater than 5 microns), produced by coughing or sneezing, or contaminated surfaces.
It says that airborne transmission is possible only after medical procedures which produce tiny aerosols, or dry particles smaller than 5 microns, that remain suspended in the air.
Benedetta Allegranzi, the organization's technical lead for infection prevention and control, has claimed that the evidence suggesting airborne transmission in "crowded, closed, poorly ventilated settings cannot be ruled out."
This could bring major changes in COVID-19 prevention measures.
While WHO has not confirmed the case of airborne transmission, it sure has acknowledged it is a possibility.
The evidence, the agency officials caution, is preliminary at this stage, and would have to be assessed further to be fully sure if the airborne transmission is happening or not.
More details might be shared around this in the coming days.
The shift in position comes just a few days after 239 experts from 32 countries wrote an open letter to the agency, claiming that there is strong evidence of COVID-19 transmission.
"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," said University of Colorado's chemist Jose Jimenez.
As virus-carrying respiratory droplets are larger and mostly water, they fall on the surface after being released.
But, in the case of airborne transmission, the tinier infected aerosols release into the air while talking or exhaling and might float around for hours, "glide the length of a room," according to the experts who plan to publish their evidence in a scientific journal this week.
If airborne transmission of COVID-19 is confirmed, the WHO may change its preventive guidelines and recommend widespread use of masks and more stringent social distancing, especially in closed public places and transport.
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