Speaking in a confined environment can cause airborne virus transmission, likely helping to spread the coronavirus, according to new research. 

The study team used a highly sensitive laser to see and count microdroplets generated by a participant speaking into a box. They found that loud speech can emit thousands of oral fluid droplets per second that remain airborne for more than 10 minutes. 

Meanwhile, each minute of loud speech can generate more than 1,000 coronavirus-containing droplets, the investigators estimated. The particles are small enough to reach the lower respiratory tract when inhaled by another person, an event that is tied to a higher risk of adverse disease outcomes, wrote Valentyn Stadnytskyi, Ph.D., from the National Institute of Diabetes and Digestive and Kidney Diseases.

Other coronavirus transmission studies have suggested that coughing, sneezing and even singing in confined spaces may increase the risk of coronavirus transmission. In an informal review of the latest evidence, one epidemiologist proposed that exposure to more particles or exposure for a longer duration multiplies the chances of transmission. Other factors include droplet velocity (a sneeze is said to travel 200 miles per hour), and air flow (an enclosed space increases exposure), wrote Erin Bromage, a researcher from the University of Massachusetts Dartmouth.

Notably, other studies have shown that respiratory droplets released from breathing contain low levels of virus when compared to sneezing and coughing. These more forceful actions expel “huge amounts of viral material,” wrote Bromage.

Once it’s in the environment, the coronavirus can survive for up to three hours in the air and three days on surfaces, a previous study has found.

The current study was published in the journal Proceedings of the National Academy of Sciences.