Scientists in South Korea say a woman on a flight from Milan was infected with the coronavirus, probably from the plane’s bathroom.
For its cohort study, the researchers enrolled 310 passengers who boarded an evacuation flight from Milan to South Korea, on March 31, when Italy was at the height of its coronavirus outbreak.
“This evacuation flight was conducted under strict infection control procedures by the Korea Centers for Disease Control and Prevention (KCDC), based on the guidelines of the World Health Organization (WHO),” the scientists wrote in an early release article submitted to the Centers for Disease Control and Prevention in Atlanta.
As the cohort arrived at the Milan airport, they underwent physical exams and medical interviews, and had their temperature checked. Eleven of the 310 were showing symptoms of COVID-19 and were removed from the flight.
The remaining 299 passengers were issued N95 respirators, which they removed only to eat and when going to the bathroom, and were seated 6½ feet apart. When they arrived in South Korea, the passengers were placed in isolation for 14 days, with no contact with one another.
All were tested on the first and 14th days of quarantine. Six passengers were positive for COVID-19 on day 1 and were sent to the hospital. They showed no symptoms on day 14, and were categorized as asymptomatic.
On day 14, a 28-year-old woman tested positive for COVID-19. The only time she removed her mask during the 11-hour flight was when she used the toilet, which she shared with passengers near her. Among those was one of the six who were asymptomatic, meaning they had the coronavirus but never showed symptoms. The woman did not go outside and had self-quarantined alone for three weeks before the flight.
Considering the woman didn’t use public transportation to get to the airport, the scientists wrote, it is highly likely her infection was transmitted during the flight via indirect contact with an asymptomatic patient. The remaining 292 passengers were released from quarantine on day 15, and all crew members tested negative.
“Because KCDC performed strong infection control procedures during boarding; the medical staff and crew members were trained in infection control; all passengers, medical staff, and crew members were tested twice for SARS-CoV-2; and a precise epidemiologic investigation was conducted,” the scientists wrote, “the most plausible explanation for the transmission of SARS-CoV-2 to a passenger on the aircraft is that she became infected by an asymptomatic but infected passenger while using an onboard toilet.”
The team said its research provides evidence of asymptomatic transmission of COVID-19 on an airplane. “Further attention is warranted to reduce the transmission of COVID-19 on aircraft. Our results suggest that stringent global regulations for the prevention of COVID-19 transmission on aircraft can prevent public health emergencies.”
