Transmission of Covid-19 on flight into Ireland linked to 59 infections

Inflight transmission of Covid-19 may have resulted in the infection of 59 people across the State, including 13 passengers on the same long-distance flight, according to a new study.

The outbreak occurred despite low levels of occupancy on the long-haul flight, the fact that different groups of passengers who tested positive were not sitting near each other and the fact that most were wearing masks, the study notes.

The authors say the outbreak demonstrates the potential for the spread of Covid-19 linked to air travel.

Onward transmission from the 13 passenger cases resulted in a total of 59 cases in six out of the eight HSE health regions across the country, necessitating national oversight of the outbreak.

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The 13 passengers, ranging in age from one to 65 years, had transferred to an Ireland-bound flights via a large international airport, having flown into Europe from three different continents.

One group of cases reported spending up to 12 hours overnight in the transit lounge during stopover; another shared a separate transit lounge; while two other groups had separate short waits of under two hours in the general airport departure area.

Low occupancy

The flight into Ireland was 7½ hours long and had a passenger occupancy of 17 per cent, with just 49 out of 283 seats occupied, and 12 crew.

The study, published in Eurosurveillance journal, suggests the high number of cases could be linked to “high intensity of infection and high viral shedding” in the index case, which was not identified.

Inflight transmission is a plausible exposure for some of the cases that occurred on the flight, and the only common exposure for others, according to the research by a team of HSE public health doctors.

Between two and 17 days passed before symptoms showed among the cases.

Eleven passengers on the flight could not be contacted, and one declined to be tested.

The study says swift action is needed where cases with no other link emerge beyond the close contact two-seat radius usually applied in investigating outbreaks involving air passengers.

“Stringent on-board infection prevention and control measures are vital to reduce the risk of both symptomatic and asymptomatic in-flight transmission.”

At the time of the outbreak, the 14-day incidence of the disease in Ireland was under 5 cases per 100,000 people; today, it is over 300.