A report published by members of Ireland’s Department of Public Health suggests that 59 cases of COVID-19 infection over the summer, including one ICU admission, were tied to a single long-haul flight arriving in the country over the summer. While stopping short of explicitly confirming the transmission on the plane, the report notes “the potential for in-flight/airport transmission exists in this outbreak.”
In-flight transmission is a plausible exposure for cases in Group 1 and Group 2 given seating arrangements and onset dates. One case could hypothetically have acquired the virus as a close household contact of a previous positive case, with confirmed case onset date less than two incubation periods before the flight, and symptom onset in the flight case was 48 h after the flight. In-flight transmission was the only common exposure for four other cases (Flight Groups 3 and 4) with date of onset within four days of the flight in all but the possible tertiary case. This case from Group 3 developed symptoms nine days after the flight and so may have acquired the infection in-flight or possibly after the flight through transmission within the household.
Only 17% of seats were occupied during the flight and most passengers wore masks on board. Still, 13 of the 49 passengers eventually tested positive; at least nine reported to be wearing masks throughout the flight.
They also transmitted the virus to 46 other people in Ireland. In one case a passenger transmitted it to a family member who then infected 25 of 34 other people in a shared accommodation facility.
Are masks and social distancing enough?
The researchers acknowledge existing reports suggesting “distancing and restricted crew/passenger interaction can contribute to prevention of COVID-19 transmission in-flight.” At the same time, the group notes, “It is interesting that four of the flight cases were not seated next to any other positive case, had no contact in the transit lounge, wore face masks in-flight and would not be deemed close contacts under current guidance from the European Centre for Disease Prevention and Control (ECDC).”
The country used the incident as the catalyst for increasing its restrictions, including informing all passengers when a positive case is reported on board and emphasizing Ireland’s 14-day restriction-of-movement policy for nearly all international arrivals.
Moreover, the researchers provided additional recommendations:
- When a positive COVID-19 case is linked to a flight, rapid flight contact tracing may prevent onward spread and we support the proposed EU digitalised public health passenger locator form and development of improved systems of tracing.
- Swift action is needed where cases with no other link emerge beyond the close contact two-seat radius to instigate early investigation and control measures.
- Enhanced surveillance should include transiting/transfer information to identify potential common links.
The flight in question appears – based on the seat map, cabin capacity and flight duration – to have been an A350-900 operated by Qatar Airways from Doha to Dublin.
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