Article Text
Abstract
Introduction Screening for influenza in arriving airline passengers and follow-up of people seated near passengers with suspected infection was used in New Zealand during the containment stage of the H1N1 pandemic in 2009. However, there is little evidence for in-flight transmission of influenza in modern commercial aircraft. This investigation aimed to assess the risks of such transmission from a school group of infected passengers who arrived in New Zealand on 25 April 2009.
Methods We interviewed and obtained nasopharyngeal swabs and/or serological specimens from the school group. Passengers in the same section of the aircraft were interviewed and nasopharyngeal swabs collected from those who were symptomatic.
Results All 24 members of the school group were interviewed and had nasopharyngeal swabs and/or serological specimens collected. We obtained interview information from 97 out of 102 other passengers in the rear section of the aircraft. Nine laboratory-confirmed symptomatic cases of H1N1 infection occurred in the school group. Two other passengers seated within two rows of the infected passengers developed confirmed infection, 12 and 48 h following the flight, implying an infection risk of 3.5% for the 57 susceptible passengers in those rows. Follow-up by public health workers located 93.1% of passengers, but only 52.2% within 72 h of arrival.
Conclusions This investigation suggests a small but definite risk of pandemic influenza transmission during modern commercial air travel. This risk was concentrated close to infected symptomatic passengers. It is slow and difficult to follow-up and screen exposed passengers once they have left the airport.