It has dismissed the possibility of airborne transmission, except for certain high-risk medical procedures, like when patients are first put on breathing machines.
However, on Tuesday, a group of 239 scientists in 32 countries had penned an open letter to the Geneva-based agency, outlining evidence that they say shos floating virus particles can infect people who breathe them in.
India's infection numbers have skyrocketed since the government eased lockdown restrictions and as testing has ramped up to more than 200,000 samples a day.
The updated information came after hundreds of scientists and engineers drafted an open letter to the World Health Organization demanding it changes its stance on transmission, which had said the virus was spread by droplets that are much larger and heavier, and fall through the air faster, than aerosols.
Benedetta Allegranzi, the WHO's technical lead for infection prevention and control, said that evidence emerging of airborne transmission of the coronavirus in "crowded, closed, poorly ventilated settings that have been described, can not be ruled out".
Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, said on Thursday that evidence on airborne transmission of COVID-19 still needed to be confirmed. However, the latest guidance reinforces the need for the people to compulsorily wear masks, maintain personal hygiene and follow social distancing. Van Kerkhove later qualified her comments, emphasizing that asymptomatic spread is possible but happens with unknown frequency.
Ryan cites countries like New Zealand that have declared themselves coronavirus-free, only to report new infections later as an example.
As per the Johns Hopkins University, a total number of 12,294,117 people globally have tested positive of coronavirus and 555,531 deaths have been reported so far.
"Infected people can transmit the virus both when they have symptoms and when they don't have symptoms", the agency said.
The WHO has maintained that current evidence suggests that transmission of SARS-CoV-2 occurs primarily between people through direct, indirect, or close contact with infected people through infected secretions such as saliva and respiratory secretions, or through their respiratory droplets, which are expelled when an infected person coughs, sneezes, talks or sings.
However, analysts note that the World Health Organization as a multilateral organisation lacks enforcement authority over its member countries and relies on information provided by these nations.