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BMJ. 2010 May 21;340:c2424. doi: 10.1136/bmj.c2424.

Transmission of pandemic A/H1N1 2009 influenza on passenger aircraft: retrospective cohort study.

Author information

  • 1Department of Public Health, University of Otago, Box 7343 Wellington South 6242, New Zealand. michael.baker@otago.ac.nz

Abstract

OBJECTIVES:

To assess the risk of transmission of pandemic A/H1N1 2009 influenza (pandemic A/H1N1) from an infected high school group to other passengers on an airline flight and the effectiveness of screening and follow-up of exposed passengers.

DESIGN:

Retrospective cohort investigation using a questionnaire administered to passengers and laboratory investigation of those with symptoms.

SETTING:

Auckland, New Zealand, with national and international follow-up of passengers.

PARTICIPANTS:

Passengers seated in the rear section of a Boeing 747-400 long haul flight that arrived on 25 April 2009, including a group of 24 students and teachers and 97 (out of 102) other passengers in the same section of the plane who agreed to be interviewed.

MAIN OUTCOME MEASURES:

Laboratory confirmed pandemic A/H1N1 infection in susceptible passengers within 3.2 days of arrival; sensitivity and specificity of influenza symptoms for confirmed infection; and completeness and timeliness of contact tracing.

RESULTS:

Nine members of the school group were laboratory confirmed cases of pandemic A/H1N1 infection and had symptoms during the flight. Two other passengers developed confirmed pandemic A/H1N1 infection, 12 and 48 hours after the flight. They reported no other potential sources of infection. Their seating was within two rows of infected passengers, implying a risk of infection of about 3.5% for the 57 passengers in those rows. All but one of the confirmed pandemic A/H1N1 infected travellers reported cough, but more complex definitions of influenza cases had relatively low sensitivity. Rigorous follow-up by public health workers located 93% of passengers, but only 52% were contacted within 72 hours of arrival.

CONCLUSIONS:

A low but measurable risk of transmission of pandemic A/H1N1 exists during modern commercial air travel. This risk is concentrated close to infected passengers with symptoms. Follow-up and screening of exposed passengers is slow and difficult once they have left the airport.

PMID:
20495017
[PubMed - indexed for MEDLINE]
PMCID:
PMC2874661
Free PMC Article
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