This case series assessed a commercial airline flight from Tel Aviv, Israel, to Frankfurt, Germany, that occurred on March 9th, 2020. Among 102 passengers on a Boeing 737-900 aircraft were 24 members of a tourist group. Starting 7 days earlier, the group had contact with a hotel manager who later received a diagnosis of coronavirus disease 2019 (COVID-19). No member of the group had received a diagnosis of COVID-19 before the flight, and no measures to prevent transmission (eg, wearing of masks) had been applied. The flight duration was 4 hours 40 minutes.
At the destination airport, we conducted a medical evaluation of the tourist group, including testing for severe acute respiratory syndrome coronavirus (SARS-CoV-2) in a throat swab specimen. In addition, we contacted all passengers 4 to 5 weeks later by phone and conducted structured interviews. Passengers were asked whether they had contact with a person with COVID-19. They were prompted to report symptoms and asked about previous testing for SARS-CoV-2. A semiquantitative SARS-CoV-2 IgG antibody test (EUROIMMUN) was offered to all passengers who had been seated within 2 rows of the index cases and to those who reported to have been symptomatic. Borderline and positive results in the IgG test were confirmed with a plaque reduction neutralization test (PRNT). Oral informed consent was obtained from all study participants, and additional written consent was obtained for laboratory tests. This study was exempt from a formal ethics committee approval by the University Hospital Frankfurt, Goethe University, Frankfurt, Germany.