Respiratory infections including influenza are a common cause of acute short-term morbidity
in travellers and yet the risk of these infections is poorly defined.
Objectives: To estimate the incidence density of and risk factors for acute respiratory infections (ARIs)
and influenza in Australian travellers to Asia.
Study design: Travel-clinic attendees were prospectively identified and completed questionnaires (demographic
data, travel itinerary, health and vaccination history) and also provided pre and post-travel
serological samples for Influenza A and B (complement fixation test). Returned travellers with an ARI
provided nasopharyngeal specimens for RT-PCR identification of respiratory viruses.
Results: In this cohort (n = 387) of predominantly (72 ) short-term travellers, 58 were female, the median
age was 37 years and 69 were tourists. ARIs occurred in 109 travellers (28 ) translating to an incidence
of 106.4 ARIs per 10,000 traveller days (95 confidence interval CI 88.6?126.7). The traveller type of
missionary or aid worker was a risk factor for acquiring an ARI (p = 0.03) and ARIs occurred early (<30
days) in the travel period (p = 0.001). Four travellers (1 ) acquired influenza A during travel translating
to an incidence density of 3.4 infections per 10,000 days of travel (95 CI 1.4?8.6). Influenza vaccination
was reported in 49 of travellers with a 3.5-fold higher incidence of influenza in unvaccinated travellers
compared to vaccinated travellers (p = 0.883).
Conclusions: This is one of the largest prospective studies estimating the incidence of respiratory infections
in travellers. These findings have important implications for practitioners advising prospective travellers
and for public health authorities.