When the WHO has just announced that the Covid-19 epidemic may “never go away”, this is a new worrying element.
A study shows that the coronavirus may well be transmitted not only by coughing or sneezing, but even by speaking.
Speech-generated saliva microdroplets can hang in the air of a closed space for more than ten minutes, according to an experiment published in the journal on Wednesday PNAS and which highlights the likely role of microdroplets in the Covid-19 pandemic.
Researchers at the National Institute of Diabetes and Digestive and Kidney Diseases spoke to a person in a closed box, inside which a laser was projected. Each droplet emitted passed through the laser visibly, which made it possible to quantify their number over time.
In the experiment, the person repeated, with a loud voice, “Stay healthy” for 25 seconds. The droplets remained in the air for an average of 12 minutes.
Speaking louder creates fewer droplets
Taking into account the known concentration of coronavirus in saliva, scientists estimate that loud speech can generate the equivalent per minute of more than 1,000 contaminated droplets capable of remaining suspended in the air for 8 minutes or more, in a closed space.
“This direct visualization demonstrates that normal speech generates droplets in the air that can remain in suspension for tens of minutes or more, and are eminently capable of transmitting a disease in a confined space,” conclude the researchers.
In works published in April in the journal NEJM, the same team observed that speaking louder produced relatively fewer droplets.
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