Researchers find speech-borne coronavirus can stay in the air

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Linda Silvetti serves Bart Whitehead at the opening of the Floridian restaurant on May 18, 2020 in Fort Lauderdale, Florida.

Joe Raedle | Getty Images

A recent study by researchers at the National Institutes of Health found that speech-released coronavirus particles can stay in the air for 8 to 14 minutes, indicating that airborne transmission may be even more common than never thought before.

While it has long been recognized that coughing and sneezing can transmit respiratory viruses through droplets, it is less known that just talking regularly produces thousands of droplets of oral fluid, scientists said. origin of the study.

“There is a high probability that speaking normally will cause airborne viruses to be transmitted in confined environments,” concluded the research, published in last week’s edition of the National Academy of Sciences Proceedings.

“Speech droplets generated by asymptomatic carriers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are increasingly being considered as a likely mode of disease transmission”, the study entitled “Duration of life in air of small speech droplets and their potential importance in the transmission of SARS-CoV-2, “found.

And those who speak loudly are at greater risk: “Very sensitive scattering observations of laser light have revealed that loud speech can emit thousands of droplets of oral fluid per second,” he said.

Although Covid-19 is less deadly than SARS, it is much easier to transmit, and scientists are still struggling to understand how far it can spread and how long it can survive. This information has huge ramifications for how we interact with each other and what types of spaces and activities are considered safe.

The researchers used a closed environment, with stagnant air, and found that the droplets cease to be visible after 8 minutes to 14 minutes, which, according to them, “corresponds to droplet nuclei of about 4 µm (micrometers ) in diameter, or from 12 µm to 21 µ droplets before dehydration. One um, or micrometer, equals one millionth of a meter. The coronavirus is even smaller than that – an incredibly small 0.125 µm.

The speed and length of stay of droplets in the air also depend on various factors, including the speaker’s volume, age and the dryness of the speaker’s mouth.

“Speech droplets generated by asymptomatic carriers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are increasingly being considered as a likely mode of disease transmission,” the study found. “Very sensitive scattering observations of laser light have revealed that loud speech can emit thousands of droplets of oral fluid per second. “

Public transport and poorly ventilated premises are considered high risk areas for this type of transmission. Scientific studies continue to produce new and sometimes variable results on the rapidly spreading coronavirus – scientists from Princeton University, UCLA and the National Institutes of Health reported in the New England Journal of Medicine that the virus could survive up to three hours in the air “after aerosolization. “

And a team of researchers from the Beijing Academy of Military Medical Sciences has found that droplets can be up to 13 feet, which means that recommendations for social distancing by several six-foot governments may not be sufficient.

States are grappling with this information as they try to balance the reopening of their economies after months of foreclosure and keep their people safe. The respiratory virus has infected more than 4.8 million people worldwide and killed more than 300,000 people.

Funding for the National Institutes of Health comes primarily from the annual appropriation law of the ministries of labor, health and social services, education, and related organizations.

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