On 2 March, one symptomatic (COVID-19) passenger caused a large cluster of cases during long-haul flight VN54 between London Heathrow, United Kingdom and Hanoi, Vietnam, a new study published (early) by the American Centers for Disease Control and Prevention (CDC) revealed.
The 27-year-old woman unknowingly spread on board, way before the obligation 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.
CDC traced 217 passengers and crew to their final destinations and interviewed, tested, and quarantined them. 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.