One of the easiest ways that the new coronavirus, COVID-19, spreads is through respiratory droplets produced by talking, coughing or sneezing. That was part of the reasoning behind the Center for Disease Controls’ decision to recommend that Americans wear face masks in public, and the early push for social distancing.
Now, a new study shows just how easily those droplets can spread. Researchers found that talking at normal levels can cause people to expel small respiratory droplets that hang in the air for at least eight minutes, which could explain the high rates of COVID-19 infection.
The study, from researchers at the National Institute of Diabetes and Digestive and Kidney Diseases and the University of Pennsylvania and published in a peer-reviewed journal, used laser lights to see how many droplets hung in the air after talking.
Speaking at normal levels produced droplets that stayed in the air for at least eight minutes, and loud talking emitted even more droplets.
“Highly sensitive laser light scattering observations have revealed that loud speech can emit thousands of oral fluid droplets per second,” the researchers found.
These smaller droplets can hang in the air for longer than large droplets, which sooner fall to the ground.
While the study was not specifically on COVID-19 or other viruses, the researchers said that the droplets produced by talking could be enough to infect another person.
"This study builds on earlier research by the same team showing that speaking may factor into transmission of SARS-CoV-2 and adds support to the importance of wearing a mask, as recommended by the CDC, in potentially helping to slow the spread of the virus," a spokesperson from the National Institute of Diabetes and Digestive and Kidney Diseases told USA TODAY.
There are some limitations, though. The study was conducted indoors, and did not look into whether respiratory droplets disperse faster outside, where there is greater air circulation.
Dr. Benjamin Neuman, a virologist at Texas A&M University-Texarkana who was not involved in the research told The Washington Post that the study is “the most accurate measure of the size, number and frequency of droplets that leave the mouth during a normal conversation and shower any listeners within range.”
And Dr. Andrew Noymer, an epidemiologist at the University of California at Irvine who was also not involved, agreed, telling the Post that the study provides a warning about the risks from simply talking.
“Speech creates droplets that breathing alone does not. That much is clear,” Noymer said. “Big mouths of the world, beware. You’re putting the rest of us at risk.”
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