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The controversy over whether COVID-19 is transmitted by aerosols continues, now with a letter published by Science, in which scientists say “there is overwhelming evidence” that inhalation of SARS-Cov-2 “represents a major route” of disease transmission.
The letter is signed by scientists from several American universities, like those of San Diego, Maryland, Virginia Tech and headed by Kimberly Prather, of the University of La Jolla.
Although there is agreement that COVID-19 is transmitted through large droplets of saliva that we expel when coughing or sneezing, there is still no unanimity if the contagion is also produced by aerosols, that is, much smaller droplets that can travel further and remain suspended in the air for longer.
Aerosol viruses “can remain suspended in the air for many seconds or hours, like smoke, and be inhaled”, they are also “highly concentrated near an infected person, so they can more easily infect people who are nearby,” they say.
But, in addition, aerosols containing infectious viruses “can also travel more than (two meters) and accumulate in poorly ventilated indoor air, leading to overspread events. “
Therefore, in addition to the use of masks, the safety distance and hygiene efforts, The researchers urge those responsible for public health to “articulate the importance of moving activities abroad, improve indoor air using ventilation and filtration, and improve the protection of high-risk workers. “
It is important that people wear masks “at all times in public buildings and confined spaces “, not just when a safe distance cannot be maintained.
“It is not just an academic question, but a point that will help reduce transmission if public health officials offer clear and forceful guidance on this, “says Linsegy Marr, another of the signatories and Virginia Technological University, quoted in a statement.
The purpose of this letter, Prather notes, “is to make it clear that the SARS-Cov-2 virus travels through the air and that people can be infected by inhalation. “
For this reason, he considers that “it is important to recognize” this transmission route “so that efforts are focused on cleaning the air and providing guidance on how to avoid risky indoor environments.”
But, in addition, the authors propose to seek a consensus in the controversy about transmission by aerosols and note the “urgent need to harmonize discussions on modes of virus transmission across disciplines, to ensure more effective control strategies and provide clear and consistent guidance to the public.”
Thus, they write that the scientific community must clarify the terminology used in relation to aerosols and droplets, and to use a more modern size threshold, rather than the existing one based on work from the 1930s.
The proposal to distinguish between aerosols and droplets is to take as a measure the size threshold of 100 micrometers instead of the traditional 5 micrometers.
This size – they consider – “more effectively separates its aerodynamic behavior, the ability to be inhaled and the effectiveness of interventions “.
Those responsible for public health “they should make a clear distinction between droplets expelled by coughing or sneezing “ and the aerosols that they claim can carry the virus over “much greater” distances.
Viruses in aerosols smaller than 100 microns, they say, can remain airborne in a confined space for extended periods of time. and accumulate in poorly ventilated air, leading to transmission.
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