“On the flight from Milan, Italy, to South Korea, she wore an N95 mask, except when she used a toilet,” they wrote.
“The toilet was shared by passengers sitting nearby, including an asymptomatic patient. She was seated three rows away from the asymptomatic patient,” they added.
The South Korean officials who organized the flight had put into effect full infection control measures and tested everyone before they boarded. All the passengers and crew were quarantined when they got to South Korea, as well. Six passengers tested positive soon after arrival in South Korea.
The 28-year-old woman developed symptoms eight days after she got home and was hospitalized.
“Given that she did not go outside and had self-quarantined for three weeks alone at her home in Italy before the flight and did not use public transportation to get to the airport, it is highly likely that her infection was transmitted in the flight via indirect contact with an asymptomatic patient,” the researchers at Soonchunhyang University College of Medicine in Seoul wrote.
There has been very little evidence about whether people can catch coronavirus on a flight, although many airlines have policies leaving more space for passengers, are cleaning aircraft more frequently, and are encouraging passengers to stay in their seats and not move about the aircraft. Evidence already shows aircraft ventilation systems clean the air quickly and thoroughly.
“This study was one of the earliest to assess asymptomatic transmission of COVID-19 on an aircraft. Previous studies of inflight transmission of other respiratory infectious diseases, such as influenza and severe acute respiratory syndrome, revealed that sitting near a person with a respiratory infectious disease is a major risk factor for transmission similar to our own findings,” the researchers wrote.
The researchers said the officials organizing the flight took many precautions.
“When the passengers arrived at the Milan airport, medical staff performed physical examinations, medical interviews, and body temperature checks outside the airport before boarding, and 11 symptomatic passengers were removed from the flight,” they wrote.
Passengers got N95 respirators — masks shown to protect the wearer for viral infections — and were kept six feet apart before boarding.
“Most passengers wore the N95 respirators except at mealtimes and when using the toilet during the flight. After an 11-hour flight, 299 asymptomatic passengers arrived in South Korea and were immediately quarantined for two weeks at a government quarantine facility in which the passengers were completely isolated from one another. Medical staff examined them twice daily for elevated body temperature and symptoms of COVID-19.”
They were seated near the back of the aircraft, directly across the aisle from seven passengers who later turned out to have been infected.