HOW IS COVID PREVENTED? So: how it is transmitted Sars-Cov2? Looking at the indications coming from governments and institutions around the world, the situation does not seem so clear. Too often, in fact, we have focused almost exclusively on avoiding close contacts and contaminated surfaces, forgetting what is, instead, one of the most important interventions to reduce the risk of contagion: the ventilation of closed environments. But why isn’t this the first anti-Covid commandment then? Guilt, we read in an editorial just published in the British Medical Journal, of some confusion regarding the concept of ‘airborne’ or airborne transmission, a term that has maintained an ambiguity of meaning for decades even among experts, which the pandemic has decided to bring to light without too many compliments.
Particles in the air
We all know, in fact, that the respiratory diseases they are transmitted (at least primarily) by air. But what do we mean by this term? If we think of diseases such as influenza and cold we refer to the fact that speaking, sneezing or coughing the droplets of saliva containing the virus (called droplets in English) can pass from a sick person to a healthy person placed at a short distance (a meter or two), infecting him. But for other diseases it is not so simple: it is known for example that the tuberculosis and measles they can also be transmitted with only (prolonged) stay in a patient’s room. This is because the evaporation of the droplets of saliva produced by breathing (or talking, sneezing, etc …) creates microscopic particles that can travel further and remain in suspension for a very long time (even several hours) in closed and non-ventilated environments, able to pass through looser masks such as surgical masks and to cause an infection when they are breathed in long enough.
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Air transmission
In a technical sense, it is this second avenue of contagion that specialists reserve the name of air transmission (airbone in English), but both in English and in Italian the two types of contagion are often indicated with the same word, generating a linguistic and conceptual ambiguity that did not help in the fight against the coronavirus. If some experts in fact immediately warned that Sars-Cov-2 could probably also infect through droplets nuclei (and therefore also remotely in closed environments), the indications of the health authorities instead took precious months before starting to consider the thing, limiting itself to recommending the usual preventive measures recommended for the control of the flu and other respiratory viruses. And if masks, hand sanitization and spacing are useful in both cases, when dealing with airborne viruses, another precaution is also essential: ventilate the rooms properly. A point on which – write the authors of the British Medical Journal editorial – still does not pay due attention in many international guidelines. And which instead will have to become central if we want to learn to live with the virus in the coming years.
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“The fact that there has been a lack of clarity on the issue I would say is clear – he comments Francesco Forastiere, epidemiologist, professor at Imperial College London and Scientific Director of the journal Epidemiology and Prevention. – The airborne transmission (ed. aerial) is certainly not something we discover today, yet a wait-and-see position was chosen on this aspect, which meant that what in many contexts was instead the main way of transmission of Sars-Cov-2 was not addressed. The fault is probably also of the WHO, which inexplicably waited until last December before officially recognizing Covid 19 as an airborne disease “.
Air sanitation
Today – assures Forastiere – the scientific consensus regarding the transmission of Sars-Cov-2 through core droplets is undoubted, but we continue to see the promotion of interventions of much more marginal (if not practically no) utility such as the sanitization of surfaces and floors, while emphasis on indoor ventilation is still minimal. “The indications received at Easter were in some way emblematic: lunches and dinners and visits to relatives indoors were allowed, without particular indications regarding the ventilation of the rooms in the presence of strangers, while Easter Monday outdoors, where the risks of contagion are minimal by respecting the rules, it has been prohibited. These contradictory indications probably create confusion in the population, and lead to underestimate one of the main routes of contagion, and to create an erroneous sense of security when respecting the spacing and use of the mask , while staying for long periods in non-ventilated areas “.
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