Transmission of pandemic (H1N1) 2009 influenza on international flights – Australia 2009

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

2. Background • Emergence of influenza H1N1 variant – Mexico/USA – March 2009 • WHO pandemic level 5 - 29 April 2009 • Australian response phases initiated 29 April 2009 • 2.35 million passengers by air – Mexico  164 countries March/April 2008

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

4. 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

5. Methods • 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

6. Case Definitions • 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

7. Total passengers identified from 2 flights n = 738 Contact details either insufficient or not available n = 143 (18%) Total potential passengers contacted n = 603 (82%) 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

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

9. Results - pH1N1 transmission on aircraft

10. 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

11. 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

12. 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) 2009 • 44% of passengers negative for pandemic (H1N1) 2009 • 66% of passengers with ILI but not tested for pandemic (H1N1) 2009