DAVIS, Calif. — Individuals who aren’t showing symptoms of the coronavirus can still produce enough aerosolized particles by speaking normally to transmit infections, according to researchers at the University of California, Davis. However, the research team is still unsure as to just how prominent a role speech plays when it comes to the spread of the virus.
Aerosols are tiny particles that travel through the air invisibly. Speaking creates a large number of aerosols from respiratory particles, prior research has shown.
“[L]ong ago it was established that ordinary breathing and speech both emit large quantities of aerosol particles. These expiratory particles are typically about 1 micron in diameter, and thus invisible to the naked eye; most people unfamiliar with aerosols are completely unaware that they exist,” the authors write. “The particles are sufficiently large, however, to carry viruses such as SARS-CoV-2, and they are also in the correct size range to be readily inhaled deep into the respiratory tract of a susceptible individual.”
The authors of the current work conducted a study in 2019 showing that more particles are produced the louder one speaks. Their research also showed that some people are “superemitters,” meaning they produce up to ten times as many particles as others.
In their latest study, the researchers looked to calculate how easily viruses spread through tiny droplets produced by speech. Virus particles infect lung fluids, which form into droplets. In order to find out how fast the coronavirus can spread via speech, researchers need to know how many viruses are required to trigger an infection in the body. They also need to know how far droplets can travel once expelled from the body, as well as how they’re affected by air motion in a space, and how quickly they settle onto surfaces.
More research into this information is needed to determine just how much speech affects the overall spread of coronavirus. “The stakes for the world are enormous. The aerosol science community needs to step up and tackle the current challenge presented by COVID-19, and also help better prepare us for inevitable future pandemics,” the authors conclude.
The study was published in the journal Aerosol Science and Technology.