A teen got COVID-19 from a woman who stood 20 feet away for just 5 minutes

• A high-school student in South Korea became infected with COVID-19 within just five minutes of sitting 20 feet away from an infected person, a new study found.
• The epidemiological team behind the study used cellphone data, video footage, genome sequencing, and even a re-creation of the situation to come to their conclusion.
• The finding demonstrates that infectious respiratory droplets can travel farther than 6 feet; in this case, they were propelled by the restaurant's airflow.

When a high-school senior in Jeonju, South Korea, tested positive for COVID-19 in June, public-health professionals were befuddled. The city hadn't had a case in two months, and the province hadn't had a case in one month.

The girl hadn't traveled out of town in weeks, mostly shuttling between home and school. So where, and from whom, did she get infected?

After a detailed investigation, an epidemiological team concluded the student had contracted COVID-19 while dining at a restaurant. An out-of-town business visitor, who subsequently tested positive for COVID-19, had stopped by.

The two overlapped for only five minutes, and they remained 20 feet apart. They never talked or even touched the same doorknob.

The finding illustrates that the standard definition of dangerous close contact - within 6 feet for at least 15 minutes - is not necessarily safe, especially for indoor settings, and should not be seen as protective.

The investigators used phone data, credit-card records, and even a re-creation of the situation

To conduct their investigation, which was published on November 23 in the Journal of Korean Medical Science, the team used interviews, medical history, credit-card records, video footage, and cellphone data.

They also re-created the situation in the restaurant, measuring the airflow, which was about the equivalent of a blowing fan. The restaurant didn't have windows open or the type of ventilation system that can help disperse COVID-19 particles.

The epidemiologists concluded the student was infected via respiratory droplets that were propelled along by the restaurant's airflow. Another diner along the flow's trajectory was also infected, but those with their backs to the breeze were not.

Genomic testing solidified their conclusion, as the three patients' genetic types matched.

"Incredibly, despite sitting a far distance away, the airflow came down the wall and created a valley of wind. People who were along that line were infected," Dr. Lee Ju-hyung, an epidemiologist and one of the authors of the study, told the Los Angeles Times. "We concluded this was a droplet transmission, and beyond" 6.6 feet, Lee added.

Indoor dining was deemed dangerous in part because of the potential of aerosol transmission

Other cases of coronavirus transmission happening through the air at distances farther than 6 feet have alarmed health experts because they suggest that tiny virus particles, called aerosols, can linger in a space, perhaps even after an infected person has left, Insider's Hilary Brueck reported.

But this study found that respiratory droplets traveled 20 feet, which is especially worrisome since they are the central way the virus transmits.

Dr. Megan Murray, an infectious-disease expert at Harvard, previously told Insider that while any dining outside the home comes with risk, eating outside in the sun with a decent breeze at a to-go-style restaurant is among the safest.

"Very crowded spaces without good ventilation, like bars," are the most dangerous, Murray said.