In early March, one symptomatic (COVID-19) passenger caused a large cluster of cases during long-haul flight VN54 between London Heathrow and Hanoi, Vietnam, a new study published by the American Centers for Disease Control and Prevention (CDC) revealed.
The 27-year-old woman on a Vietnam Airlines flight unknowingly spread the coronavirus before passengers were obligated to wear a face mask. The study shows how the female traveller – who had a sore throat before the flight – infected twelve business class passengers, two in economy and one crew member. There were a total of 217 people on board. The most likely route of transmission during the flight is aerosol or droplet transmission, hence the importance to wear facial coverings when close contact is unavoidable.
To assess the role of in-flight transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), CDC investigated a cluster of cases among passengers on this 10-hour commercial flight. Affected persons were passengers, crew, and their close contacts.
217 passengers and crew were traced to their final destinations and interviewed, tested, and quarantined. Among the 16 persons in whom SARS-CoV-2 infection was detected, 12 (75%) were passengers seated in business class along with the only symptomatic person (attack rate 62%). Seating proximity was strongly associated with increased infection risk (risk ratio 7.3, 95% CI 1.2–46.2).
The CDC found no strong evidence supporting alternative transmission scenarios. In-flight transmission that probably originated from 1 symptomatic passenger caused a large cluster of cases during a long flight. Guidelines for preventing SARS-CoV-2 infection among air passengers should consider individual passengers’ risk for infection, the number of passengers travelling, and flight duration.
The CDC released the article early ahead of the November publication, and is not considered as the final version. Any changes will be reflected in the online version in the month the article is officially released.
The authors of the study report include National Institute of Hygiene and Epidemiology, Hanoi, Vietnam (N.C. Khanh, P.Q. Thai, H.-L. Quach, N.-A.H. Thi, T.N. Duong, L.T.Q. Mai, N.D. Nghia, T.A. Tu, D.D. Anh); Hanoi Medical University, Hanoi (P.Q. Thai, T.-T. Nguyen); Australian National University, Canberra, Australian Capital Territory, Australia (H.-L. Quach, N.-A. H. Thi, F. Vogt); Ministry of Science and Technology, Hanoi (P.C. Dinh); Ha Noi University of Public Health, Hanoi (L.N. Quang); and Ministry of Health, Hanoi (T.D. Quang).