The new coronavirus can survive for several hours outside the human body, on various surfaces or even in the air, according to a study published Tuesday, March 17.
The authors of this study funded by the United States government found that the virus responsible for the Covid-19 epidemic had a level of viability in the open air comparable to that of the coronavirus causing SARS (severe acute respiratory syndrome).
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This could mean that the magnitude of the Covid-19 pandemic – far greater than that of SARS in 2002-2003 – is linked to the fact that it is much more easily transmitted from an asymptomatic (“healthy”) carrier to a other.
The study was published by the New England Journal of Medicine (NEJM) and conducted by scientists from the Centers for Disease Control and Prevention (CDC), the University of California Los Angeles, and Princeton.
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Their experiments showed that the new coronavirus was detectable for up to two to three days on plastic or stainless steel surfaces, and up to 24 hours on cardboard.
The researchers also used a nebulizer to spread the virus to ambient air. Using this technique, they found traces of the virus in the form of an aerosol – that is, particles suspended in the air – for three hours.
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Put online for professionals before being examined by a reading committee, the study had however drawn criticism, experts judging that the use of a nebulizer did not simulate cough or sneezing well. ‘a patient and risked artificially increasing the extent of contamination by air.
The virus is mainly transmitted by micro-droplets expelled by patients when they cough or sneeze, and in this form (different from an aerosol) it is only viable for a few seconds.
Similar tests with the SARS coronavirus have resulted in equivalent viability outside the human body.
“Aerosols are not a particularly valid model of transmission,” said Professor Paul Hunter of the British University of East Anglia. “The droplets fall quickly compared to aerosols and therefore the risk is mainly to stand about a meter from someone who is infected or by touching surfaces on which these droplets have fallen. So the advice is always not to get too close to possible cases and wash your hands regularly. “
In contrast, the longer-term persistence of the coronavirus on different surfaces “is not surprising,” notes William Keevil, professor of environmental health at the British University of Southampton, noting that other similar coronaviruses had the same characteristics.
These potential differences, however, do not explain why the Covid-19 pandemic affects nearly 200,000 people, with some 8,000 deaths, while SARS infected only 8,000 patients and killed 800.
The epidemiological differences “likely stem from other factors, such as a higher viral load in the upper respiratory tract” and the ability of symptomless patients to transmit the new coronavirus, the study authors say.
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