An official from the World Health Organization (WHO) has admitted that it cannot be excluded that coronavirus may spread through the air, in particularly crowded and poorly ventilated indoor environments. This possibility had already been reported by several researchers a few months ago, but the WHO has so far not expressed itself explicitly on the topic, waiting to have more scientific data and evidence. However, it is not clear if and when the WHO will change its guidelines on the prevention of COVID-19, integrating details on the spread of coronavirus through the air.
In recent days, an international group of 239 researchers from 32 different countries had written one open letter, arguing that there was now enough scientific evidence to believe that in some cases the virus could spread in the air. The letter had been widely taken up by the media, leading to several questions to the WHO, which until yesterday had not spoken extensively on the subject.
During a press conference, the WHO manager for technical aspects in the prevention and control of infectious diseases, Benedetta Allegranzi, he said that on the basis of the evidence that emerged “it cannot be excluded” that “in crowded, closed and poorly ventilated environments” the transmission of the coronavirus by air can take place.
A statement in a press conference does not correspond to an immediate change in the guidelines, but the fact that it has been discussed is further confirmation of the existence of a discussion on the topic. Until now, WHO had indicated that drops of saliva (droplet) that we emit when we cough, sneeze, sing or speak loudly are projected into the air at medium distance, and which can then settle on the surfaces. THE droplet produced by infected people contain millions of viral particles inside them, which could infect other individuals either directly – if some droplet reaches their mouth, nose or eyes – or indirectly, if they deposit on surfaces that are then touched from someone else, who brings his hands to his face.
For this reason, the WHO has among its guidelines the advice to wash your hands often and well, in order to reduce the risk of contagion, and suggests wearing a mask in cases where it is not possible to practice social distancing. THE dropletin fact, they can travel in the air for a few meters, before settling on the surfaces.
The research carried out in recent months however, they found circumstances in which the infection can occur by air through much smaller drops of saliva and which remain suspended in the air for a long time (aerosol). These microscopic droplets with coronavirus can be inhaled and could cause contagion in particular circumstances.
In the open air, where the concentration of aerosols is low, it is very difficult that you can contract coronavirus even if you pass near an infected person. THE risks are more high in the event that a closed environment is shared with an infected person for several minutes: in the absence of adequate air exchange, one remains exposed to a greater quantity of viral particles, suspended in the air, and consequently there is a higher risk of getting infected.
The researchers who studied these dynamics they say that in addition to the exchange of air, another risk factor to be evaluated is the exposure time. If you stay in a room with an infected person for a few minutes, the risk is lower than those who stay there for a long time. Some studies have also evaluated how particular air currents, for example induced by air conditioning systems, can affect the spread of coronavirus in a closed environment and consequently on the methods of contagion.
The WHO will continue to evaluate the studies conducted so far on the spread of coronavirus through the air, and will need several days before deciding whether to modify or maintain the current guidelines, which indicate as more relevant the direct contagion or through surfaces on which aerosols have settled. A change in the guidelines would also imply the addition of advice on how to reduce the risk of infection, especially in hospital environments, where it is not always possible to guarantee a good exchange of air. There could also be consequences for means of transport that have closed ventilation systems, such as airplanes and various passenger train models.
Over the past few months, the WHO has revised and integrated its guidelines several times, sometimes receiving criticism for the slowness with which it has done so. Having to coordinate the work of hundreds of health institutions around the world, the WHO proceeds with great caution, especially on aspects still under debate and discussion in the scientific community.
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