The WHO confirms: the coronavirus is not transmitted by air, but only by saliva droplets

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Carlos Laforet Coll
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There is no airborne transmission, the virus only passes through the respiratory droplets that an infected person throws when he sneezes or coughs.

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There is no airborne transmission of the virus, but only through contact with saliva droplets from an infected person. This is confirmed once again by the World Health Organization, which in a study analyzes the forms of transmission of the coronavirus, confirming that it it only passes through the respiratory droplets that an infected person throws when he sneezes or coughs. There is virtually no evidence of airborne transmission.





It goes without saying, concludes the WHO, that masks are not strictly necessary for those who are going out of the house for a moment (dog, garbage ...) and above all it recommends leaving the filtering ones to health personnel and to those who work closely with sick people.

Respiratory infections, experts explain in the paper, can be transmitted through droplets of different sizes: when the droplet particles have a diameter greater than 5-10 μm they are called "respiratory droplets"; when they are less than 5μm in diameter they are "droplet nuclei".

According to current data, the Covid-19 virus is mainly transmitted between people through respiratory droplets. Likewise, we read, in an analysis carried out on 75.465 Covid-19 cases in China airborne transmission was not reported.

Droplet transmission occurs when a person is in close contact (within 1 meter) with someone who has respiratory symptoms (for example, coughing or sneezing) and is therefore at risk of having their mucous membranes (mouth and nose) or conjunctivae (eyes ) exposed to potentially infectious respiratory droplets. Transmission can also take place through fomiti (we speak of fomites when the source of contagion is contact with contaminated material, for example infected needles, stethoscope or thermometer, clothing or towels, which, passing from the sick to the healthy person, produces the infection) in the surrounding environment around the person infects.

Therefore, the WHO says, the transmission of the Covid-19 virus can occur by direct contact with infected people and indirect contact with surfaces in the immediate environment or with objects used on the infected person.

“Airborne transmission differs from droplet transmission as it refers to the presence of microbes within droplet nuclei, which are generally considered to be particles <5μm in diameter, can remain in the air for long periods of time and be transmitted to others. for distances greater than 1 m ”, they explain.



Why then do some studies speak of a transmission in the air?

The answer is given by the WHO itself. To date, some scientific publications had in fact provided initial evidence that the coronavirus could be detected in the air and, therefore, some news agencies had suggested that there was an airborne transmission. These initial results, they say, need to be interpreted carefully and for all it comes to studies not yet published and carried out in laboratory environments.

This is the case of a recent publication in the New England Journal of Medicine, for example, which assessed the persistence of the virus in the air. In this experimental study, the aerosols were generated using a Collison's three-jet nebulizer and placed under controlled laboratory conditions.

"This is a high powered machine that does not reflect normal human cough conditions."

Furthermore, the discovery of the Covid-19 virus in aerosol particles up to 3 hours does not reflect a clinical setting in which aerosol generation procedures are performed, i.e. this was an experimentally induced aerosol generation procedure.

In the context of Covid-19, WHO reiterates, airborne transmission may only be possible in specific circumstances and contexts where supportive procedures or treatments that generate aerosols are performed: ie endotracheal intubation, bronchoscopy, open aspiration, administration of nebulized treatment, manual ventilation before intubation, disconnection of the patient from the ventilator, non-invasive positive pressure ventilation, tracheostomy and cardiopulmonary resuscitation. Nothing that concerns those who do not work in the healthcare environment, in short. It is for this reason that WHO recommends the use of certified masks only for those in close contact with the infected.

HERE the complete study by the World Health Organization.



Fonte: OMS / New England Journal of Medicine

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