(CNN) — The young woman and her sister traveled through Europe just as the coronavirus pandemic was taking off there, visiting Milan and Paris before heading to London.
When the woman left London on March 1, she had a sore throat and a cough while boarding a flight back to Vietnam, but no one noticed.
When she got off the flight in Hanoi 10 hours later, 15 other people who had been on the plane with her were infected, the researchers reported Friday.
This story is one of two published on Friday that demonstrate how the coronavirus can spread on airline flights and suggests that simply spacing people a little won’t fully protect them.
In another incident, passengers on a flight from Boston to Hong Kong appear to have infected two flight attendants.
Both cases involved long flights at the beginning of the pandemic, before airlines began requiring face masks.
A team from Vietnam tracked down a cluster of cases related to the flight that arrived in Hanoi from London on March 2.
“A 27-year-old businesswoman from Vietnam, whom we identified as the probable index case, had been based in London since the beginning of February,” wrote Nguyen Cong Khanh of the National Institute of Hygiene and Epidemiology in Hanoi and colleagues.
“On February 22, Case 1 and her sister returned to Milan, Italy, and subsequently traveled to Paris, France, for the annual Fashion Week before returning to London on February 25,” they wrote in the magazine. Emerging Infectious Diseases.
At this time, the coronavirus was beginning to spread rapidly in Italia, but very few cases had been reported in Great Britain.
The woman boarded a flight to Hanoi on March 1.
“She was sitting in business class and continued to experience a sore throat and cough throughout the flight,” the researchers added.
He went to a hospital three days after landing and tested positive for the virus. Health officials tracked down 217 passengers and crew who had been on the flight with her and found that 12 business classmates, two economy class passengers and a crew member were also infected.
The researchers said there was no other likely way the other 15 could have been infected other than exposure to the sick patient on the flight.
“The most likely route of transmission during flight is the aerosol or droplet transmission of Case 1, particularly for people seated in business class,” they wrote.
“We conclude that the risk of transmission on board SARS-CoV-2 during long flights is real and has the potential to cause sizable covid-19 clusters, even in business-class environments with spacious seats far beyond the established distance. used to define close contact in airplanes, ”Khanh’s team wrote.
“As long as covid-19 poses a global pandemic threat in the absence of good testing at the point of care, better infection prevention measures on board and arrival screening procedures are needed to make flying safe.”
Cases traced with genetic sequencing
In the second incident, a couple flew from Boston to Hong Kong in business class on March 9. They both showed symptoms upon arrival and were diagnosed with coronavirus.
Contact tracing found that two flight attendants also tested positive for the virus. “The only place where the four people were in close proximity for an extended period was inside the plane,” wrote Deborah Watson-Jones of the London School of Hygiene and Tropical Medicine and her colleagues in a second report in the journal Emerging Infectious Diseases from the US Centers for Disease Control and Prevention.
«Genetic sequencing linked the four cases. The nearly complete viral genomes of the four patients were 100% identical, “Watson-Jones and colleagues noted.