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The past July 5, a group of 239 scientists sent a letter to the World Health Organization (WHO), asking it to reconsider its guidelines according to which the coronavirus is not transmitted by air. The experts argued that there is considerable evidence that the pathogen can infect through small aerosols, and that is not only is transmitted when two people are close to and speak or sneeze without the use of the mask, expelling large particles of aerosols. WHO assessed these arguments, but their official response was that there was not enough evidence that the viruses that float in the aerosol small to be viable and able to infect.

Now, a group of scientists has managed to prove precisely that the viruses that float in the aerosols are viable and infective . In a pre-publication, not yet peer-reviewed, researchers from the University of Florida, in the united States, have presented evidence that there is virus viable in the air up to a distance of five feet of patients infected with COVID-19, far beyond the separation of two metres recommended by the social distancing measures.

“This is proof that people were claiming,” he said to her, “The New York Times” Linsey Marr , an expert in viral diseases of airborne transmission is not involved in the work. “This is unequivocal evidence that there is virus infective in those aerosols”. “If this is not the definitive test,” said Marr on Twitter, “then I don’t know what can be”.

José Antonio López Guerrero , a virologist from the Center of Molecular Biology Severo Ochoa (CBM-CSIC) has recommended to maintain prudence in the face of these results: “it is Always better to be cautious than to leave the possibility of the transmission distance without studying,” he commented to ABC. “But it is necessary to confirm these results in other environments and by other research groups. Their implications on the safety distances would be very important.”

Viruses ability to infect cells

at The beginning of the pandemic, it was observed that the presence of the virus viable in rooms of patients COVID-19 was low. Finally it was concluded that the SARS-CoV-2 that is spread about everything from aerosol particles large , increased to five micrometers (a micrometer is one-thousandth of a millimeter), which limits their duration in the air and your “reach” from an infected person. Logically, this could explain their low presence in the air of the rooms where there are patients.

Another possibility is that the process of capture of the aerosols, to make experiments, to damage the virus and make them lose their power infective. That’s why, on this occasion the scientists desarrollararon a new technique to capture the aerosols and to transfer its contents to a liquid rich in salts, sugar and protein, with the aim of preserving the pathogens.

The researchers collected air samples in rooms dedicated to patients COVID-19 in the hospital’s Health Shands, University of Florida. None of the patients was submitted at that time to treatments able to generate aerosols, a pathway that from the beginning of the pandemic, the WHO considered to be a form of tramisión air in hospital environments.

To evaluate the “scope” of the aerosols, collected samples at two and five metres from the patients, and then checked if the content of the drops was sufficient to infect cells in a lab plate .

Layout of the rooms and the instruments for collecting aerosols used in this study – Lednicky et al., 202074 the virus per milliliter of air

Thanks to this, the scientists detected a total of 74 virus per milliliter of air. As the air of the room is changed once every six hours and facilities Health Shands are equipped with ultraviolet radiation and other measures to inactivate the virus, virologist John Lednicky has said that it is expected that in spaces that are worst-ventilated build up many more virus .

on the other hand, the virologist Angela Rasmussen has said in “The New York Times” doubt that such a concentration of virus sufficient to infect someone : “The only conclusion that I can draw from this article is that you can grow virus viable in the air. Which is no small thing.”

how Enough the two meters of distance?

For Robyn Schofield , atmospheric chemistry, University of Melbourne, in Australia, the most relevant of the study is that this implies for the recommendations to maintain the social distance: “ we Know that in confined spaces, these distances can no longer be used “.

as mentioned, an aerosol can pass through a room in five minutes, even if the air is still. Therefore, according to her, the safety distance “is misleading, because people think that they are protected indoors, when really it is not”.

Seema Lakdawla , an expert in respiratory viruses at the University of Pittsburgh, these findings should make is to put attention on measures such as the improvement of the ventilation: “we All know that this virus can spread all of these ways, but we’ve only focused on a small part.”

Until now, the WHO has focused on the transmission of the virus via large particle aerosols expelled from infected people up to a moderate distance. Therefore, according to Lakdawala, the more distance you can keep, the better. For the moment, it is unknown how many viruses would be needed, and in what conditions, for producing an airborne contagion.

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