In a letter written to the World Health Organisation, 239 scientists have put forth evidence to show that smaller particles of the novel coronavirus in the air can infect people, asking for a revision in its recommendations, The New York Times reported on Sunday, 5 July.

The WHO has maintained that the virus spreads primarily by large respiratory droplets that quickly fall on the floor once an infected person sneezes, coughs or speaks. However, with significant evidence for smaller or bigger particles remaining in the air, the safety and precautionary protocols would have to be updated to cater to airborne transmission as well.

Bill Hanage, an epidemiologist at the Harvard TH Chan School of Public Health, said,

But experts claim that SARS-CoV-2 doesn’t necessarily behave the same way, and may, in fact, be most infectious when people are in prolonged contact at close range - indoors as well as in superspreader events - which is just on the lines of aerosol transmission, meaning that the virus lingers in the air, NYT reported.

Dr Benedetta Allegranzi, the WHO’s technical lead on infection control, called the evidence for airborne transmission ‘unconvincing’ and said, “Especially in the last couple of months, we have been stating several times that we consider airborne transmission as possible but certainly not supported by solid or even clear evidence. There is a strong debate on this.”

However, scientists believe the organisation is relying on a more ‘outdated’ understanding of ‘airborne’, differentiating between tiny aerosols and larger droplets, even though an infected person produces both. Instances of the virus spread in poorly ventilated and crowded indoors show that the virus could be transmitted through the air.

Linsey Marr, an expert in airborne transmission of viruses at Virginia Tech, is quoted in the NYT as saying,

While the WHO has long been focusing and pushing for hand-washing to prevent the spread of the virus through surfaces, these experts believe face-coverings and ventilation systems will have to be given equal importance as precautionary measures if the airborne spread is acknowledged.

Dr Trish Greenhalgh, a primary care doctor at the University of Oxford in Britain, told the NYT, “There is no incontrovertible proof that SARS-CoV-2 travels or is transmitted significantly by aerosols, but there is absolutely no evidence that it’s not. So at the moment, we have to make a decision in the face of uncertainty, and my goodness, it’s going to be a disastrous decision if we get it wrong. So why not just mask up for a few weeks, just in case?”

The letter is expected to be published in a scientific journal next week.

(With inputs from The New York Times)