The woman had a sore throat and cough when she boarded a flight home in Vietnam when she left London on March 1, but no one noticed.
As she disembarked from a flight in Hanoi 10 hours later, 15 other people on the plane with her became infected, investigators reported Friday.
The story, one of two published on Friday, shows how coronaviruses spread on airline flights, and suggests that keeping people a short distance away will not save them safely.
In another incident, two flight attendants were infected by passengers on a flight from Boston to Hong Kong.
Before the need for face masks was introduced by airlines, long episodes involved long flights in both cases.
The Vietnamese team found a cluster of cases linked to a flight from London to Hanoi on March 2.
“The 27-year-old Vietnamese businessman, whom we have identified as a potential index case, has been based in London since the beginning of February,” Cong Kang Khan and his colleagues wrote.
The woman was aboard a flight to Hanoi on March 1.
“She was placed in business class and had been experiencing sore throats and cuffs throughout the flight.”
She went to the hospital three days after landing and tested positive for the virus. Health officials found 217 passengers and crew on the flight with him and found 12 fellow business class passengers, two economy class passengers and a crew member infected.
Investigators said none of the other 15 people on the flight were likely to have been infected, except for contact with a sick patient.
The most likely mode of transmission during a flight is an aerosol or dot transmission from Case 1, especially for persons sitting in business class, they wrote.
“We conclude that the risk of SARS-Cavi-2’s on-board transmission during long flights is real and that even in the business class, large-sized COVID-19 clusters are likely to form – such as settings with seating arrangements for spaces.” Established distances were used to determine air contact, “Khan’s team wrote.
“Better on-board infection prevention measures and arrival detection procedures are needed to make the flight safe as long as COVID-19 poses a global epidemic threat in the absence of a good point of care.
In another incident, on March 9, a couple flew from Boston to Hong Kong in business class, after which they both showed symptoms and were diagnosed with coronavirus.
“The genetic index combined all four cases. The near-full-length viral genomes of all four patients were 100% identical,” Watson-Jones and colleagues wrote.
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