Home / News / India /  Covid-19 may spread via speech, says study

The novel coronavirus can spread through droplets emitted when an infected person speaks, according to new research on the virus’ alarming efficiency of transmission. So far, public health specialists had focused on coughing and sneezing as the most potential mediums of transmission of SARS-CoV-2.

Now, scientists from the National Institutes of Health (NIH), US, have come up with troubling new evidence of transmission in confined spaces. They used an intense sheet of highly sensitive laser light to visualize bursts of small-sized droplets produced during repeated spoken phrases. The droplets are too small to be seen, but are large enough to carry pathogens that can linger in the air “for tens of minutes or longer" before shrinking and eventually disappearing.

The research points at the risk of transmission in enclosed spaces as the experiment was conducted in a confined environment.

According to scientists, speaking produces about 2,600 droplets per second, which corresponds to an estimated 2.4-12 nanolitres of airborne oral fluid. In case of covid-19, the oral fluid has a high viral load, even in asymptomatic cases. “Now assuming that oral fluid contains approximately 7 million SARS-CoV-2 copies per mL (millilitre) in covid-19 infected persons, then that 1 minute of loud speaking could generate more than 1,000 virus-containing droplets that will remain airborne for 8 minutes or longer," the study said.

“These observations confirm that normal speaking in enclosed environments might carry a substantial risk of virus transmission." The findings were published in the journal Proceedings Of National Academy Of Sciences.

Once airborne, these speech-generated droplets rapidly dehydrate due to evaporation, and start decreasing in size which delays their fall. “Our laser light scattering method not only provides real-time visual evidence for speech droplet emission, but also assesses their airborne lifetime. This demonstrates how speech generates airborne droplets that can remain suspended and are capable of transmitting disease in confined spaces," said the team.

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