Researchers analyze in-flight transmission of pandemic influenza A 2009 (H1N1)

Foxwell AR. Emerg Infect Dis. 2011;17(7):in press.

Sitting two seats in front of, two seats behind or within two seats on either side of an index pandemic influenza A 2009 (H1N1) case patient on an airplane may increase the risk for developing the infection later, according to study results.

Researchers from several sites in Australia conducted a retrospective cohort study to determine whether in-flight transmission of pandemic influenza A 2009 (H1N1) occurred on two flights entering Australia in May 2009.

The analysis involves combined results of survey responses from 319 of the 738 (43%) passengers on the two flights. Results indicated that 2% of that sample had influenza-like illness in-flight, and 5% of that sample developed influenza-like illness within a week of arriving.

Sitting in the same row or within two rows of those who were symptomatic before the flight carried a 3.6% increased risk for developing H1N1.

A closer exposed zone was described as two seats in front, two seats behind or two seats on either side of a symptomatic passenger. Those sitting in closer exposed zones were at a 7.7% increased risk for developing H1N1 after the flight.

The flights were chosen after eight passengers on the first flight — which departed in Los Angeles and arrived in Sydney — were identified as having confirmed influenza A 2009 (H1N1). The second flight originated in Singapore and carried one confirmed H1N1 case patient.

“Efficiency of contact tracing without compromising the effectiveness of the public health intervention might be improved by limiting the exposed zone,” the researchers wrote.

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