- A new study shows that a person talking loudly can emit tiny droplets that carry the novel coronavirus, which can then float for several minutes in the air.
- The research offers proof that social distancing and the use of face masks can protect people from infection.
- The findings can also explain how asymptomatic patients might transmit the virus without sneezing or coughing.
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Microscopic droplets containing the novel coronavirus help the virus spread to others with ease. We’ve known this for months, and that’s why hand-washing, social distancing, and the use of protective gear such as face masks are all required. If those droplets reach your eyes, mouth, or nose, you can get infected. And you don’t even have to inhale droplet-filled air for it to happen. Those droplets can land on surfaces after a sneeze or a cough and that’s how the virus can infect you. But there’s increasing evidence that suggests just speaking is enough to spread the virus, and a new study provides more proof.
In the past few weeks, we saw a few experiments that supported the same idea. Larger droplets will travel in the air up to 6 feet, and they’ll land on surfaces — and air conditioning will carry them well beyond those 6 feet that are deemed as safe. But micro-droplets that are ejected while a person is talking can linger in the air for a more extended period, especially in rooms that aren’t well ventilated. And these aerosols might be enough for an infected person to pass COVID-19 to others.
Researchers from the National Institute of Diabetes and Digestive and Kidney Diseases and the University of Pennsylvania used lasers and cameras to record those tiny droplets and assess their behavior in the air. They found that loud speaking can emit plenty of droplets per second, which will linger in the air for several minutes:
Highly sensitive laser light scattering observations have revealed that loud speech can emit thousands of oral fluid droplets per second. In a closed, stagnant air environment, they disappear from the window of view with time constants in the range of 8 to 14 min, which corresponds to droplet nuclei of ca. 4 μm diameter, or 12- to 21-μm droplets prior to dehydration.
The study acknowledges that the cameras can’t catch every small particle that can be ejected while a person is speaking, and it explains that the viral load in saliva can vary from patient to patient. On average, the researchers say that one minute of loud speaking generates at least 1,000 virion-containing droplet nuclei that remain airborne for more than 8 minutes. But some people may eject as many as 100,000 virions per minute of loud speaking. Many of those tiny particles are small enough to reach the lower respiratory airways when inhaled by someone else.
This study and similar work that we’ve already seen can’t say for certain that loud speaking can emit enough of a viral load to infect others. But the evidence it provides is enough to support the idea that COVID-19 transmission is possible via speaking. Also, the study would explain how asymptomatic patients can spread the disease without having to sneeze or cough.
Researchers not involved in the study agree with the findings. “This 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,” Benjamin Neuman told The Washington Post. Neuman is a virologist at Texas A&M University-Texarkana.
He continued, “This study doesn’t directly test whether the virus can be transmitted by talking, but it builds a strong circumstantial case that droplets produced in a normal close conversation would be large enough and frequent enough to create a high risk of spreading SARS-CoV-2 or any other respiratory virus between people who are not wearing face masks.”
With all that in mind, wearing some sort of face mask when you’re out of the house is definitely a necessity. Also, remember to keep your distance from other people and wash your hands as often as possible.
The study has been peer-reviewed and it’s available over at the Proceedings of the National Academy of Sciences. The accompanying video can be downloaded at this link. You’ll be looking for green dots against a black background (as seen on the right in the image above). Those are the droplets emitted during speech, as captured by the camera after being lit with the laser.