The versions of the coronavirus that all seven carried were genetically virtually identical – strongly suggesting that one person among them initiated the outbreak. This person, who the report calls Passenger A, actually had a negative test four or five days before boarding, the researchers found.
Jan. 7, 2021, 10:17 p.m. ET
“Four or five days is a long time,” said Dr. Kamar. “Ideally, you should ask about the results of rapid tests done hours before the flight.”
Even restrictive “Covid-free” flights, international bookings that require a negative result, give people a day or two before departure to get a test.
The results are not final, warned the authors, led by Dr. Tara Swadi, an advisor to the New Zealand Ministry of Health. However, the results “underscore the value of considering all international passengers arriving in New Zealand as potentially infected, even with pre-departure testing, social distancing and separation and personal protective equipment used during the flight,” the concluded Researcher.
Previous studies of the risk of infection in air travel have not clearly quantified the risk and it is believed that on-board air filtration systems reduce the risk of infection among passengers, even if a flight involves one or more infected people. However, at least two recent reports strongly suggest in-flight outbreaks pose a risk: a flight from Boston to Hong Kong in March; the other from a flight from London to Hanoi, Vietnam, also in March.
On the flight to Hong Kong, the analysis found that two passengers boarding in Boston infected two flight attendants. On the flight to Hanoi, the researchers found that 12 out of 16 people who later tested positive were in business class and that proximity to the infectious person strongly predicted the risk of infection.
Airlines’ policies vary widely, depending on the flight and airline. During the first few months of the pandemic, most US airlines had a policy of blocking seats or rescheduling passengers if a flight was nearly 70 percent full. However, during the holidays, those guidelines were largely ditched, said Scott Mayerowitz, editor-in-chief at The Points Guy, a website that covers the industry.