The versions of the coronavirus that all seven carried were virtually identical genetically — strongly suggesting that one person among them initiated the outbreak. That person, whom the report calls Passenger A, had in fact tested negative four or five days before boarding, the researchers found. Previous studies of infection risk during air travel did not clearly quantify the risk, and onboard air filtration systems are thought to reduce the infection risk among passengers even when a flight includes one or more infected people. On the Hong Kong flight, the analysis suggested that two passengers who boarded in Boston infected two flight attendants. On the Hanoi flight, researchers found that 12 of 16 people who later tested positive were sitting in business class, and that proximity to the infectious person strongly predicted infection risk.

Source: International New York Times January 07, 2021 22:51 UTC