"The available data indicates that it is much more common for the virus to be spread through close contact with someone with Covid-19 than through airborne transmission." This little phrase disappeared from the official website of the Centers for Disease Control and Prevention (CDC), the major US health agency, on Friday. It is now stated - in bold - that the airborne virus can be inhaled even when one is more than two meters from an infected individual. The expression "close contact", for "close contact", is no longer used. "They got rid of some old problematic terms," said the New York Times scientist Linsey Marr, professor at Virginia Tech.
This change is not trivial.
It further certifies the risk of transmission of SARS-CoV-2 by aerosol, which took time to impose itself among the authorities and even within the scientific community.
We are talking about "micro-droplets of very small size which float in the air for several hours and can permanently contaminate the atmosphere of a room", describes the virologist Yves Gaudin.
"Scientific evidence"
Like several scientists, this researcher from the Institute for Integrative Cell Biology (I2BC) of Paris-Saclay believes that this mode of contamination represents a “major” part of infections.
“We saw that people had been infected in different hotel rooms by the ventilation system, and that people were able to infect others in public transport while they were at the other end of the road. bus.
These are very striking evidence, ”he illustrates.
On April 15, six researchers working in the United States or the United Kingdom detailed in the journal The Lancet ten "scientific evidence" according to which SARS-CoV-2 was "mainly transmitted by air".
Airborne it is.
🦠
The 10 streams of overwhelming evidencehttps: //t.co/y3ZT40Nsu8@TheLancet by @trishgreenhalgh @ kprather88 @Rschooley @zeynep @jljcolorado @dfisman
a 5- ★ succinct summary pic.twitter.com/Ox305pSoaU
- Eric Topol (@EricTopol) April 15, 2021
For a long time, many people were not convinced of this.
At the very beginning of the pandemic, the two main transmission factors identified were large droplets, when one spits or sneezes on a person nearby, and contaminated surfaces.
Hence the repeated recommendation to wash your hands regularly, for example.
On April 4, a first warning shot was sounded by 239 scientists. In a letter to the World Health Organization (WHO), they indicated that this coronavirus would also be transmitted "through much smaller expired droplets" and that this air could "infect people when inhaled". "New evidence confirms the potential for airborne transmission of the new coronavirus, a crucial aspect to be taken into account in any device for reopening public places," reacted the international organization, while specifying that this risk was "not demonstrated ". On its site, it is still indicated in May that the virus "is spread mainly through close contact with an infected person".
Last October, the CDC had already mentioned in black and white the risk of aerosol transmission over long distances, but they reverted to previous guidelines a few hours later.
The agency had pleaded an "error" to upload, while some saw it as a sign of political pressure.
Ventilation and CO2 sensors
Throughout the fall and winter, scientists called for airborne transmission to be taken into account… and therefore to issue recommendations aimed at preventing it.
In France, the collective “On the side of science” has become very active on the subject, using the keyword “CovidIsAirborne” in abundance on social networks.
🥁 SARS-CoV-2 is transmitted first by "inhalation of very small drops and #AEROSOLS" indicates the CDC 🇺🇸 today, specifying that the understanding of transmission has evolved!
📢 #COVIDisAirborne https://t.co/ofFRx05h0N pic.twitter.com/ke8VIJBAgR
- On the Science Side (@Cote_Science) May 7, 2021
"The most effective is to open the windows and avoid gathering in closed and poorly ventilated places", insists Yves Gaudin.
The authors of the text published in The Lancet list for their part "ventilation, air filtration, reduction of time spent indoors, use of masks indoors" among the measures to be taken.
Read also Covid-19: install CO2 sensors to control ventilation, the idea that is rising
In France, because they cannot easily open the windows in the middle of winter, some establishments have also installed air purifiers (the effectiveness of which varies greatly depending on the device).
Others recommend the deployment of CO2 sensors, making it possible to be alerted when the air is not pure (and therefore potentially carrying aerosols containing the virus) and thus to optimize the window opening periods.
The website of the Ministry of Health updated in April
At the end of October, the ventilation of the rooms officially joined the list of barrier gestures recommended by the Ministry of Health.
But it wasn't until April that aerosol transmission was added to its site, as the archives show.
The virus "cannot live in the air on its own", it was indicated until then, and only the large droplets were detailed in the section "How is the Covid transmitted".
The risk of transmission by aerosol is now on the website of the Ministry of Health.
DR /
In March, in the midst of an epidemic recovery, the government's slogan even became to go outside, the complete opposite of the “stay at home” used a year earlier.
“Inside with mine, outside as a citizen”, to use the slogan used.
“Scientists realized that there was a virtual absence of contamination on the outside. Aerosols are completely dependent on the slightest draft and they are dispersed very quickly, ”emphasizes Yves Gaudin. Another sign of this awareness: on April 22, for the first time, the Minister of National Education Jean-Michel Blanquer officially recommended installing air purifiers and / or CO2 sensors in schools. .