When a high school student in Jeonju, South Korea tested positive for COVID-19 in June, public health professionals were confused. No case had occurred in the city for two months, or in the province for a month.
The girl hadn’t driven out of town for weeks, mostly commuting back and forth between home and school. So where and from whom did she get infected?
After an in-depth investigation, an epidemiological team concluded that the student had contracted COVID-19 while eating in a restaurant. An out-of-town business traveler who subsequently tested positive for COVID-19 was there.
Dangerous close contact can no longer be seen as a protective measure
The two only overlapped for five minutes and they stayed six meters apart. They never spoke to each other or even touched the same doorknob.
The result shows that the standard definition of dangerous close contact – within two meters for at least 15 minutes – is not necessarily safe, especially indoors, and should not be viewed as a protective measure.
The team used interviews, medical histories, credit card records, video footage and cell phone data for their research, published November 23 in the Journal of Korean Medical Science.
The researchers recreated the situation
They also simulated the situation in the restaurant and measured the air flow, which roughly corresponded to that of a fan. The restaurant didn’t have open windows or the type of ventilation system that can help dispel COVID-19 particles.
The epidemiologists concluded that the teenage girl was infected from drops of breath carried away by the airflow from the restaurant. Another guest along the flow path was also infected, but those with their backs to the wind did not become infected.
Genomic tests confirmed their conclusion as the genetic types of the three patients matched.
“Incredibly, even though we were sitting far away, the current of air came down the wall and created a valley of wind. People who were along this line became infected, ”said Dr. Lee Ju-hyung, an epidemiologist and one of the study’s authors, told the Los Angeles Times. “We deduced that this was droplet transmission,” over two and a half meters, Lee added.
Indoor food classified as dangerous
Other cases of coronavirus transmission through the air over distances greater than three feet have alarmed health experts because they suggest that tiny virus particles called aerosols can linger in a room, perhaps even after an infected person has left it.
But this study found that respiratory droplets traveled six meters, which is particularly worrying given that they are the central path that the virus transmits.
Dr. Megan Murray, an infectious disease expert at Harvard, told NewsABC.net that while eating outside of the home is risky, outdoor take-out is one of the safest with a good breeze.
“Very crowded rooms without good ventilation, like bars,” are the most dangerous, said Murray.
This text has been translated from English. You can find the original here.