the role of aerosols and covid-19

Covid-19: is it risky to eat in a restaurant? 4:49

(CNN Spanish) – Scientists have already established that COVID-19 is transmitted through aerosols. It was only until the end of April that the World Health Organization mentioned this form, aerosols, as a form of contagion.

What did the WHO say? Dr. Elmer Huerta explains it in this episode.

You can listen to this episode on Spotify or your favorite podcast platform or read the transcript below.

Hello, I am Dr. Elmer Huerta and this is your daily dose of information about the new coronavirus. Information that we hope will be useful to take care of your health and that of your family.

The debate about the contribution of aerosols to the spread of COVID-19 seems to be coming to an end.

The role of aerosols in contagion, according to the WHO

In its latest review on how covid-19 is transmitted on April 30, the World Health Organization specifically mentions that aerosols are a mode of contagion.

Until now, the WHO had been careful to mention the role of aerosols in the spread of the virus.

The WHO specifies that the size of the particles released from the respiratory tract varies from large respiratory droplets to microscopic aerosols.

The document mentions that the virus can spread from the mouth or nose of an infected person through thick droplets of secretions, in what they call short-range contagion generally within 1 meter of distance.

Eyes, nose and mouth, the contagion points

But, and this is the novelty, a person can also become infected, says the WHO, when aerosols or microscopic droplets containing the virus are inhaled and come into direct contact with the eyes, nose or mouth, tacitly accepting the role they play. aerosols in contagion.

That type of contagion, they say, occurs in poorly ventilated and / or crowded indoor environments, where people tend to spend longer periods of time, and where aerosols remain suspended in the air or travel more than 1 meter away, in what they call long-range contagion.

This knowledge is very important because –as we heard in the April 20 episode– the management of closed spaces is very important to avoid contagion through aerosols.

Where can aerosol contagion occur?

These places must be prepared to minimize the effect of aerosols, ensuring an adequate ventilation system:

Urban public transport, airplanes, trains, supermarkets, shops, shopping centers, private homes, hospitals, and any place that houses people,

In this sense, the multiple studies that, since the beginning of the pandemic, have emphasized that most infections occur in closed spaces and not in open spaces are very relevant.

What the studies say

One of them, published in the Journal of Infectious Diseases on February 14, 2021, reports a meta-analysis or systematic review of peer-reviewed articles, published until August 12, 2020, and in which cases of human transmission of SARS-CoV-2.

In total, twelve studies of value were identified for review, and five of them revealed that less than 10% of SARS-CoV-2 infections occurred outdoors, and that the likelihood of transmitting SARS-CoV-2 in a Indoor space was 18.7 times higher than outdoor.

Unfortunately, the authors say, the studies were very different in quality and in what was defined as an outdoor environment, limiting their ability to draw conclusions about the risks of outdoor transmission.

In general, the factors that determined the possibility of contagion were the duration and frequency of contact between people in the outdoor meetings, the use of personal protective equipment, and the fact that even though the meeting was outdoors , at some point there were occasional meetings in an enclosed space.

Sprouts and enclosed spaces

In another study, this time published in the Indoor Air magazine in May 2021, a group of Chinese researchers studied 318 outbreaks that produced 1,245 confirmed cases of covid-19 in 120 cities in China.

The location of the outbreaks was classified into six categories:

homes, transportation, restaurants, entertainment, shopping and others.

What they found was that nearly 80 percent of the 318 outbreaks – with three to four COVID-19 cases per outbreak – occurred in the home. And 34 percent originated in public transportation, with only one outbreak documented in an outdoor setting, an outbreak that produced only two cases.

In summary, and as the Chinese researchers conclude, knowing that the indoor environments in which we live and work are the most common places in which SARS-CoV-2 is transmitted, it is necessary to improve the hygienic and ventilation conditions of these environments. indoors to decrease the spread of airborne infectious diseases.

And since studies show a direct association between overcrowding and infection, we must think deeply about the need for ventilated and healthy indoor environments, even as the pandemic passes.

Do you have questions about the coronavirus?

Send me your questions on Twitter, we will try to answer them in our next episodes. You can find me at @DrHuerta.

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If you have any questions you can send them to Dr. Elmer Huerta through Twitter. You can also head over to for all episodes of our “Coronavirus: Reality vs. Reality” podcast. fiction”.