INFLIGHT TRANSMISSION OF Covid-19 may have resulted in the infection of 59 people across Ireland – including 13 passengers on the same long-distance flight – according to a new study.

The outbreak occurred despite low levels of occupancy on the flight from the Middle East to Ireland during the summer, a study published in a European journal has found. 

The paper, written by the Department of Public Health in Ireland and published by Eurosurveillance, found that 13 passengers tested positive between two and 17 days after landing in Ireland. 

The youngest passenger to test positive was 1 and the oldest was 65 -  with a median age of 23. 

The study – which does not identify the airline or departure point – found that the virus spread on the plane despite only 49 (17%) of the plane’s 283 seats being occupied. 

All 13 passengers who later tested positive transferred via a large international airport, flying into Europe from three different continents. 

One group of infected passengers spent up to 12 hours overnight in a transit lounge during a stopover, according to the study. The flight into Ireland was 7.5 hours long. 

Twelve of the 13 flight cases and almost three quarters of the 46 non-flight cases later identified were symptomatic.

The earliest onset of symptoms among the 13 passengers occurred 2 days after arrival, and the last in the outbreak occurred 17 days after the flight.

Of the 13 infected passengers, nine wore masks during the flight. The infected child did not wear a face covering while three passengers did not say whether they wore masks.

The study notes that the “source case” of the outbreak is not known and that the Department of Health set up a team to “investigate, identify and interview cases, oversee contact tracing and establish control measures.”

The study suggests the high number of cases could be linked to “high intensity of infection and high viral shedding” in the source case. 

Close contact passengers were defined as two seats in every direction from the first cases notified. 

Nine close contacts of the infected passengers initially tested positive. The remaining passengers were then offered testing where contactable.

Five more passengers then tested positive for Covid-19, 15 tested negative, and 11 were not contactable.

At the time of the outbreak, Ireland’s 14-day incidence was under 5 cases per 100,000 people. It is currently 302.91 cases per 100,000 people. 

The study notes: “Onward transmission from 13 passenger cases resulted in a total of 59 cases in six of eight HSE health regions in Ireland, necessitating national oversight of the outbreak.”

The study says “swift action” is needed where cases with no other link emerge beyond the close contact two-seat radius, which is usually applied when investigating outbreaks among air passengers. 

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

“Restriction of movement on arrival and robust contact tracing are essential to limit propagation post-flight,” the study says. 

It was announced earlier this week that the EU ‘traffic light’ system to co-ordinate international Covid-19 travel restrictions across the continent will come into force in Ireland on Sunday, 8 November.

Under the plan, the European Centre for Disease Prevention and Control will publish a weekly map of the EU using a three-stage colour system to indicate the level of risk in each area.

Levels will be determined by a variety of epidemiological factors including the 14-day incidence per 100,000 population and the level of positive tests.