A report published by members of the Irish Department of Public Health suggests that 59 cases of COVID-19 infection during the summer, including an ICU admission, were linked to a single long-distance flight arriving in the country during the summer. While stopping before explicitly confirming transmission on the plane, the report notes “the potential for flight / airport transmission exists in this outbreak”.
In-flight transmission is a plausible exposure for cases in Group 1 and Group 2, given the seating arrangements and start dates. A case could hypothetically have acquired the virus as a close family contact from a previous positive case, with confirmed start date of the case less than two incubation periods before the flight, and the onset of symptoms 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 a start date within four days of the flight in all but the possible tertiary case. This Group 3 case developed symptoms nine days after the flight and, therefore, may have acquired the infection during the flight or possibly after the flight, by transmission within the home.
Only 17% of seats were occupied during the flight and most passengers wore a mask on board. Still, 13 of the 49 passengers had positive results; at least nine reported wearing masks throughout the flight.
They also passed the virus on to 46 others in Ireland. In one case, a passenger passed it on to a family member who infected 25 of 34 others in shared accommodation.
Are masks and social distance enough?
The researchers acknowledge existing reports that suggest “detachment and restricted crew / passenger interaction may contribute to preventing the transmission of COVID-19 in flight.” At the same time, the group notes: “It is interesting that four of the flight cases were not sitting next to any other positive case, had no contact in the transit room, wore masks during the flight and would not be considered close contacts under the guidance European Center for Disease Prevention and Control (ECDC). “
The country used the incident as a catalyst to tighten its restrictions, including informing all passengers when a positive case is reported on board and emphasizing Ireland’s 14-day movement restriction policy for almost all international arrivals.
In addition, the researchers provided additional recommendations:
- When a positive COVID-19 case is linked to a flight, rapid flight contact tracking can prevent further spread and we support the EU’s digitized public health passenger tracking form and the development of improved tracking systems.
- Rapid action is required when cases without another connection emerge beyond the radius of two places of close contact to instigate investigation and early control measures.
- Enhanced surveillance should include traffic / transfer information to identify possible common connections.
The flight in question appears – based on the seat map, cabin capacity and flight duration – to have an A350-900 aircraft operated by Qatar Airways from Doha to Dublin.
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