[Effectiveness of border screening for detecting Influenza in arriving airline travelers]

We measured symptom and influenza prevalence, and the effectiveness of symptom and temperature screening for identifying influenza, in arriving international airline travelers.

This cross-sectional study collected data from travelers to Christchurch International Airport, New Zealand, in winter 2008, via a health questionnaire, temperature testing, and respiratory sampling.

Forms were returned by 15 976 (68%) travelers. Of these, 17% reported at least 1 influenza symptom, with runny or blocked nose (10%) and cough (8%) most common. Respiratory specimens were obtained from 3769 travelers. Estimated prevalence of influenza was 1.1% (4% among symptomatic, 0.2% among asymptomatic). The sensitivity of screening criteria ranged from 84% for "any symptom" to 3% for a fever of 37.8 ºC or greater. The positive predictive value was low for all criteria.

Border screening using self-reported symptoms and temperature testing has limitations for preventing pandemic influenza from entering a country. Using "any symptom" or cough would lead to many uninfected people being investigated, yet some infected people would remain undetected. If more specific criteria such as fever were used, most infected people would enter the country despite screening.