What was so far not established yet feared seems to be coming true. The World Health Organization has acknowledged “evidence emerging” of the airborne spread of the novel coronavirus.

This happened after In an open letter to the World Health Organization, at least 239 scientists from 32 countries  claimed that the Covid-19 coronavirus is airborne. The scientists plan to publish their findings in a journal this week.

Previous evidence had suggested that the virus was transmitted from person to person through droplets from the nose or mouth, which are expelled when a person with the disease coughs, sneezes or speaks.

WHO has so far emphasised that the virus can spread through the air only in case of medical procedures that produce aerosols, or droplets smaller than five microns. The global health body has instead promoted frequent hand washing as a means to keep the virus away.

Now the new finding will change the way be approach the virus is our social ecosystem and the chances of greater and faster spread increases.

WHO’s Dr Benedetta Allegranzi, however, said the evidence was unconvincing. “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,” she said. “There is a strong debate on this.”

In April, a group of 36 experts on air quality and aerosols had urged WHO to consider growing evidence on airborne transmission of the virus. The health body called Lidia Morawska, the group’s leader and a WHO consultant, for a meeting. However, at the meeting, WHO experts continued to stress the importance of hand washing.

Morawska had provided evidence of several incidents that indicated airborne transmission of the virus, contending that the WHO was making an artificial distinction between tiny aerosols and larger droplets, though infected individuals produce both.

Dr Linsey Marr, an expert in airborne transmission of viruses at Virginia Tech University in the US, said the scientific community knows since 1946 that coughing and talking generate aerosols. She said that most of the samples taken were from hospital rooms with good air flow, which dilutes viral levels.

Dr Marr also contended that WHO was relying on an outdated definition of airborne transmission – a definition that states that an airborne pathogen has to be highly infectious and to travel long distances.

For a virus to be airborne means that it can be carried through the air in a viable form. For most pathogens, this is a yes-no scenario. H.I.V., too delicate to survive outside the body, is not airborne. Measles is airborne, and dangerously so: It can survive in the air for up to two hours.

For the coronavirus, the definition has been more complicated. Experts agree that the virus does not travel long distances or remain viable outdoors. But evidence suggests it can traverse the length of a room and, in one set of experimental conditions, remain viable for perhaps three hours.

Concerns about airborne transmission of the coronavirus have intensified following a massive surge in cases in some countries, such as the United States, which has been reporting close to 50,000 new infections per day. Dr Marr said “superspreader” events can be explained by the hypothesis that the virus is airborne.

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