Alasdair Duncan 2008
The occurrence of an influenza pandemic is considered inevitable. Vaccines and antiviral medication are now commonplace for the prevention and treatment of seasonal influenza, but these are unlikely to be available in sufficient quantities to be primary strategies in the global response to the next influenza pandemic. Consequently, research and resources are being directed towards developing non-pharmaceutical interventions (NPIs) to contain or reduce the spread of pandemic influenza.
Entry screening of international airline travellers is one possible NPI that island nations may employ to prevent or limit the spread of pandemic influenza. This thesis reports on an investigation of the feasibility of using a health screening questionnaire distributed on board aircraft, collection of throat swabs, and follow-up contact to measure the prevalence of influenza in airline travellers entering New Zealand. A health screening questionnaire was developed and distributed to all passengers and crew on board five flights arriving at Christchurch International Airport from Australia. These were collected by research assistants in the International Arrivals Hall, and two groups of travellers were invited to provide a throat swab for laboratory analysis: those who were symptomatic, defined as a reporting one or more ‘core’ influenza symptoms of fever, sore throat, cough, muscle aches and pains and chills; and those who were asymptomatic and randomly selected. Asymptomatic respondents who provided consent and contact details were contacted three days after arrival to determine whether they had developed symptoms. Those who had developed symptoms were also invited to provide a throat swab.
The questionnaire was completed by 359 of 628 travellers (57%), of whom 55 (15%) were symptomatic and three (0.8%) met the influenza-like illness (ILI) case definition of fever plus cough or sore throat. Fifty-seven of 103 (55%) eligible respondents agreed to have a throat swab taken, with one confirmed influenza infection. Three days after arrival, follow-up contact was made with 121 (75%) of the consenting asymptomatic respondents, of whom 14 (12%) had developed symptoms and three had a swab taken. The pre-flight, in-flight, and airport components proved feasible and, although some difficulties were experienced during questionnaire collection and recruitment of respondents at the airport, piloting the study using five flights provided the opportunity to modify and re-trial these processes. The follow-up of asymptomatic travellers three days after arrival also proved feasible, although the limited willingness of symptomatic follow-up respondents to travel to a laboratory for swabbing suggests an active process is required if samples are required to be collected.
This thesis demonstrates that it is feasible, with some negotiation, to use a health screening questionnaire distributed on board aircraft entering New Zealand combined with a throat swab, follow-up contact, and virological analyses to measure the prevalence of influenza infection in international travellers. A larger study is planned to measure the prevalence of symptomatic and asymptomatic influenza infection in arriving international airline travellers, the predictive value of the questionnaire, and the resource requirements of routine entry screening. The recommendations of this pilot study will enable this larger study to be carried out more effectively and efficiently.