Transmission of pandemic (H1N1) 2009 influenza on international flights – Australia 2009 Acknowledgements Ruth Foxwell, Leslee Roberts, Kamalini Lokuge, Paul Kelly

Emergence of influenza H1N1 variant – Mexico/USA – March 2009 WHO pandemic level April 2009 Australian response phases initiated 29 April million passengers by air – Mexico  164 countries March/April 2008 Background

Passengers closer to index case on aircraft are most at risk Air filtration in aircraft has been upgraded Different disease  different dynamics Respiratory disease transmission on aircraft Background

Major issues Policies for passenger follow-up based on tuberculosis and SARS* Limited resources  response priorities Aim Investigate transmission of pandemic influenza (H1N1) 2009 on international flights arriving in Sydney in May 2009 *WHO technical advice for case management of Influenza (H1N1) in air transport, Geneva 2009 Background

Retrospective cohort study on flights arriving Sydney - weekend 23/24 May 2009 One from country with documented community transmission One from country with no documented community transmission Data collection Surveyed passengers 3 months following flight arrival Questions: symptoms ILI, onset date, co-morbidities, movement in-flight, other potential exposure to ILI; anti-viral prophylaxis, isolation/quarantine, contact with health professionals following flight Triangulated information with national notifications of pandemic (H1N1) 2009 Ethics approval – DoHA, ANU Methods

Influenza-like illness (ILI) At least one of cough, sore throat, headache, runny nose, muscle aches, diarrhoea, lethargy Time periods specified for: 7-14 days pre-flight, during flight, 7 days post flight Pandemic (H1N1) 2009 ILI + Laboratory confirmation Case Definitions

Total passengers identified from 2 flights n = 738 Total potential passengers contacted n = 603 (82%) Contact details either insufficient or not available n = 143 (18%) Total surveys returned n = 319 (response rate = 43%, participation rate = 53%) Results – defined population Additional 5 ILIs (23%) and 2 cases (20%) of pH1N1 identified through triangulation process

Flight 1 Flight arrival in Sydney Pre-flight ILI - infectious in-flight Results – ILI onset dates

Results - pH1N1 transmission on aircraft Disease onset of index caseProximity to index case Risk of contracting pH1N1 Before/during flight2 + 2 rows1.4% Before flight2 + 2 rows3.6% Before flight2 + 2 seats7.7%

Timeliness of Public Health Action Total passengers followed up by public health officers = 145 Survey results (from 52 of 145) 67% of people contacted by public health ≥ 3 days after flight arrival Serial interval of disease = 2.9 days(average)  Only 33% of passengers followed through in optimal time period

Summary – pandemic (H1N1) 2009 Public Health action for passengers on international flights: more timely follow-up required to effectively prevent community spread from infectious individuals travel restrictions for symptomatic individuals may be appropriate 2+2 square rather than 2+2 rows may assist in prioritizing contact tracing for influenza

Results – ILI symptom comparison Self-reporting of symptoms did not distinguish cause of ILI 50% of passengers positive for pandemic (H1N1) 2009 had fever 44% of passengers negative for pandemic (H1N1) 2009 had fever 20% of passengers with ILI but not tested for pandemic (H1N1) 2009 had fever Number of different symptoms did not distinguish cause of ILI Two or less symptoms not including fever reported for: 38% of passengers positive for pandemic (H1N1) % of passengers negative for pandemic (H1N1) % of passengers with ILI but not tested for pandemic (H1N1) 2009