More than four months since the outbreak of the novel coronavirus, not much is known about it. Researchers from around the world are studying newer characteristics of the deadly contagion that has infected close to 4.5 million people and killed over 298,000.
A group of researchers in the US has attempted to find out whether the coronavirus, also known as SARS-CoV-2, can spread through normal speech.
While speaking, oral droplets are generated. While the larger ones fall to the ground and quickly evaporate, the smaller ones persist in the air for some time, where they behave like aerosols. An experiment conducted by American researchers found that micro-droplets generated by speech can stay in the air for an average duration of 8-14 minutes. Thus, there is a "substantial probability that normal speaking causes airborne virus transmission in confined environments", according to a study published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).
For the experiment, researchers at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) had a person loudly repeat "stay healthy" for 25 seconds inside a closed box, AFP reported. The interior of the box was illuminated using a highly sensitive laser to allow the researchers to observe and count the number of droplets and determine the period after which they disappear.
The researchers found that "loud speech can emit thousands of oral fluid droplets per second". In closed, stagnant air they disappear after a period of 8 to 14 minutes, i.e. an average of 12 minutes. "High viral loads of SARS-CoV-2 have been detected in oral fluids of coronavirus disease 2019 (COVID-19)−positive patients including asymptomatic ones," the study stated.
"This direct visualization demonstrates how normal speech generates airborne droplets that can remain suspended for tens of minutes or longer and are eminently capable of transmitting disease in confined spaces," the researchers concluded.
If the infectiousness of the coronavirus through speech is determined, it'll bolster the case for wearing masks.