Washington (AFP)

In March, before masks became routine, German tourists infected with the coronavirus returned from Israel by plane, a flight lasting more than four hours during which, to the researchers' surprise, only two infections from other passengers. were discovered.

In a short study published Tuesday in the American journal Jama Network Open, virologists from the University Hospital of Frankfurt meticulously contacted all the passengers on the flight to discover the real risk posed by the presence of passengers infected with the virus responsible for Covid -19.

On March 9, the Tel Aviv-Frankfurt flight lasting 4:40 had 102 passengers on board, including a group of 24 tourists. The German authorities, having received information that the group had been in contact with a contaminated hotel manager in Israel, decided to test the 24 tourists on their arrival in Frankfurt.

Seven of them tested positive (seven more will be later).

Four to five weeks later, researchers contacted the remaining 78 passengers, 90% of whom responded. When asking them about their contacts and symptoms, and testing several of them, they found two passengers most likely infected during the flight: two people sitting across the corridor from the original seven cases.

For respiratory viruses, virologists traditionally consider that the contamination zone on an airplane extends two rows in front, and two rows behind.

But surprisingly, a person seated in the row (seat 44K) immediately in front of two infectious tourists (seats 45J and 45H) was not contaminated.

"The person in row 44 told us that she had had a long conversation with the two in row 45", however tells AFP Sandra Ciesek, director of the Institute of Medical Virology in Frankfurt.

No contamination either for two passengers sitting immediately behind another infected tourist.

"We were surprised to find only two transmissions," said Sebastian Hoehl, from the same institute.

All the other passengers were unfortunately not tested, so it cannot be ruled out that others were infected. The study confirms in all cases that transmissions in an airplane, in the absence of masks, are indeed possible.

But, underlines the researcher, "the rate being lower than expected, and none of the passengers having worn a mask, it is reassuring that we have not detected others".

And the researchers note that several studies of repatriation flights from Wuhan, China, at the start of the pandemic, established that no contamination had taken place on board, while passengers were masked.

© 2020 AFP