A body of evidence suggests that transmission of the virus into ambient air is indeed possible. The question remains debated, but, in the meantime, the United States is on the point of recommending the wearing of a generalized mask in order to limit the risks.
Americans soon encouraged to wear protective masks in public places? Possible, suggests Science magazine which understands that the American Centers for Disease Control and Prevention (CDC) is about to modify their recommendations in light of recent results suggesting that SARS-CoV-2, the virus causing Covid-19, is also reported to be transmitted into ambient air via aerosols.
While it was previously believed that the virus was mainly spread via large droplets ejected by coughing, sneezing or postillions, new studies suggest that it would also travel via air and the famous aerosols, these clouds microscopic droplets – a thousand times smaller than postillions – perfectly invisible to the naked eye.
None of the work in question here provides definitive proof. But all seem to “confirm the hypothesis of aerosolization of the virus during respiration,” reports Science magazine, citing a letter written by Harvey Fineberg, member of the American National Academy of Sciences and addressed to Kelvin Droegemeier, responsible for Office of Science and Technology Policy at the White House. So very official, and perhaps enough to bring about a review of the advice given to the population.
If corroborated, this aerosol hypothesis would be a game-changer. Large droplets do not travel very far, usually within two meters of a sick person, and then fall by gravity. Two ways of infection are therefore possible: when these postlets are directly inhaled, or when they contaminate surfaces which are then touched by fingers which will inevitably go on the mouth, nose or eyes. In both cases, social distancing and hand hygiene, mantras repeated since the start of the epidemic, are enough to minimize the risks.
But if the virus is able to float in the air for several hours, protected by tiny droplets as a recent study by the New England Journal of Medicine suggested, then protecting yourself would be much more difficult.
Another study mentioned in the letter goes in this direction. Led by a team from the University of Nebraska Medical Center, it highlights the ubiquitous presence of viral RNA in rooms intended for positive patients: in toilets, on window sills, through bed frames, approximately 75% of the surfaces tested were positive for viral RNA. The same is true in air samples, including more than two meters from patients. What lead the authors to mention a possible transmission by aerosols, even if in this experiment, the scientists did not find any infectious elements strictly speaking, the virus being in quantity a priori insufficient.
Other works appearing in this letter finally evoke the protective equipment which the nursing staff are wearing (coats, overcoats, charlottes, etc.) as potential sources of transmission. Led by a team from Wuhan University, they suggest that taking off these clothes would appear to resuspend the coronavirus in the air. Important clarification: these last two studies are awaiting validation and therefore publication. Caution is therefore required.
Put together, all these elements begin to constitute a body of evidence tending towards a possible contamination by aerosols, estimates the American academy. This could also explain the lightning spread of SARS-CoV-2. And also give voice to supporters of the widespread wearing of surgical masks in public places, which would prevent asymptomatic carriers from forming hypothetical infectious clouds.
“Masks must play a role, no doubt greater than previously thought, but be careful not to go overboard when you see the virus in all the air you breathe”, moderates Serge Kouzan, pulmonologist at the Center Métropole Savoie hospital in Chambéry.
The World Health Organization (WHO) goes in the same direction and reiterated on March 27 that aerosol transmission occurs only in very specific cases, for example when the intubation of patients in critical condition.