Infected 5 minutes after 20 feet away: According to a South Korean study, COVID-19 is infected indoors.world

The results of this study, with the help of aerodynamic technicians by Lee and other epidemiologists, were published in the Journal of Korean Medical Science last week. The conclusion raised concerns that the widely accepted 6-foot standard of social distance may not be sufficient distance to keep people safe.

In addition to increasing evidence of virus transmission in the air, the study will allow researchers to closely track how the virus moves within the population through South Korea’s meticulous and often invasive contact tracking regime. I emphasized that it became.

“In this outbreak, the distance between the infected was … farther than the generally accepted 2 meters. [6.6 foot] The extent of droplet propagation, “the author of the study wrote. “The guidelines for quarantine and epidemiological investigations need to be updated to reflect these factors for the management and prevention of COVID-19.”

People wearing face masks pass the Coronavirus Safety Banner, which advises on an enhanced social distance campaign in Seoul.

KJ Sun, an infectious disease expert and head of strategy and policy for non-profit partners in COVID response in Massachusetts Health, said the study found that many countries are seeking winter for indoor infections. He said it was a reminder of the risks. The official definition of “close contact” — within 15 minutes, 6 feet — is not absolutely certain.

In his study of Massachusetts contact tracing programs, business owners and school managers adhered to the criteria of “close contact,” considering exposure for only 14 minutes, or what in the same room more than 6 feet away. He said he spent some time. It’s safe.

“There is a real misunderstanding about this in the general public,” said Sun, who was not involved in South Korean research. “They think that if I weren’t in close contact, they would be magically protected.”

According to Sun, the study spreads the internet to look for people who may be infected and warns low-risk people that they may have been exposed to contact tracers around the world. He said he pointed out the need.

Lindsay Marr, a professor of civil engineering and environmental engineering at Virginia Tech, who studies the transmission of viruses in the air, said that a 5-minute time frame in which a student identified as “A” in the study was infected with a droplet of virus. It’s big enough to carry a quantity, but small enough to move 20 feet in the air.

“The’A’was probably provided by a larger aerosol of about 50 microns and we had to get a large dose in just 5 minutes,” she said. “Large aerosols or small droplets that overlap in that gray area can propagate the disease over a meter or two. [3.3 to 6.6 feet] When the air flow is strong. “

Korean research began with a mystery. Epidemiologists were confused when a senior high school student in Jeonju tested positive for coronavirus on June 17, as the city had not had a case of COVID-19 for two months. Jeollabuk-do, where Jeonju is located, was less than a month old. The girl hasn’t left the area for the past few weeks, mostly from home to school and back.

The contact tracer turned to the country’s epidemic research support system, a digital platform introduced in South Korea during the pandemic. This gives investigators access to the infected person’s mobile phone location and credit card data in just 10 minutes.

Mobile phone GPS data reveals that the student was temporarily duplicated with another known coronavirus patient from another city or prefecture who was a door-to-door salesperson visiting Jeonju. I did. Their connection was only 5 minutes at the restaurant on the ground floor on the afternoon of June 12.

Door-to-door salespeople visited Jeonju officials, who told a contact tracer who visited Jeonju about an hour’s drive from her company that her company had met with 80 people. The 6th floor of the building with the restaurant.

Professor Lee of JeonBuk National University School of Medicine also helped with the epidemiological investigation of the local government, and went to a restaurant and was surprised at how much they were sitting. CCTV footage showed that the two had never spoken or touched common surfaces such as door handles, cups, and cutlery. From the shaking of the lamp, I knew that the air conditioner on the ceiling was on.

Lee and his team recreated the state of the restaurant — the researchers were sitting at the table as a substitute — and measured the airflow. The third canteen, infected with a high school student, was sitting directly in the air stream from the air conditioner. The other diners who turned their backs on the airflow were uninfected. Through genome sequencing, the team confirmed that the viral genome types of the three patients were consistent.

“Unbelievably, despite sitting far away, a stream of air came down the wall, creating a valley of wind. People along that line were infected,” Lee said. Said. “We conclude that this is the propagation of droplets, which is over 2 meters.”

According to Professor Ma of Virginia Tech, who was not involved in the study, the pattern of infection in restaurants was not from aerosols, but through droplets that landed on the face. The wind speed measured in a restaurant without windows or ventilation is about 1 meter per second, which is equivalent to a fan.

“Eating indoors in a restaurant is one of the most dangerous things you can do in a pandemic,” she said. “As this shows, and as other studies have shown, distance is not enough, even if it is.”

The study, like many other countries, is at stake in a new wave of COVID-19 infections, recently published when the number of cases per day is about 600. I did. The capital, Seoul, began demanding that restaurants close by 9 pm this week, coffee shops were restricted to takeaway only, and clubs and karaoke were forced to close.

The study, similar to the July study in Guangzhou, China, examined the infection of three families who ate at a restaurant along the flow of air conditioning at a table three feet away for about an hour. .. Ten of the diners were coronavirus positive. South Korean contact tracers also planned an outbreak at Starbucks in Paju in August. Twenty-seven people were infected with a woman sitting under a ceiling air conditioning unit on the second floor.

Seung of Partners in Health said South Korean epidemiologists have helped researchers around the world better understand the epidemic of the coronavirus by following the route of infection.

“I showed it to my team doing contact tracing in Massachusetts, and their jaws are down,” Sun said. “We know how difficult it is to do such a thing — it’s impressive.”

© 2020 Los Angeles Times.Access to latimes.com.. Distributed by Tribune Content Agency, LLC.