Travel to malaria-endemic areas: using digital geo-location to assess potential exposure risks and health behaviours.

Background: Travellers frequently visit popular destinations like Brazil, India, Peru, Thailand, and Tanzania, each presenting varying malaria risks. The extent to which travellers enter high-risk malaria-endemic areas in destinations with heterogeneous malaria risk remains unclear. We used geo-location via smartphone application to (i) describe where travellers go within countries with heterogeneous malaria risk (Brazil, India, Peru, Thailand), and (ii) compare mosquito bite prevention behaviours between these destinations and Tanzania, considered entirely high-risk for malaria.

Methods: This analysis is a sub-study of the TOURIST2 cohort, which prospectively recruited 1000 travellers (≥ 18 years, travelling ≤ 4 weeks) from Swiss travel clinics (Zurich and Basel) between 09/2017-04/2019. We included 734 travellers to Brazil, India, Peru, Thailand, and Tanzania who provided geo-location data. Daily health and geo-location data were collected using a smartphone application. Malaria risk was categorised using 2022 malaria maps from the Swiss Expert Committee for Travel Medicine.

Results: Of the 734 travellers, 525 travelled to Brazil, India, Peru, and Thailand, and 225 to Tanzania. In Brazil, India, Peru, and Thailand, only 2% (n = 13) visited high-risk malaria areas. In Peru, 4% (n = 4) visited a high-risk area; in Brazil, 3% (n = 6); in Thailand, 2% when crossing the border into Myanmar (n = 3); and in India, 0%. Travellers to high-risk areas were more often male (62%), slightly older (median age 42.0), and planned longer trips (median 23.0 days) than other travellers. No participants were diagnosed with malaria. Travellers to Brazil, India, Peru and Thailand used mosquito bite prevention measures less frequently than travellers to Tanzania. Those in Tanzania had higher, but still suboptimal, use of insect spray (65% of travel-days).

Conclusions: Travellers to Brazil, India, Peru, and Thailand rarely visited high-risk malaria areas, and their adherence to mosquito bite prevention measures was generally low. In Tanzania, adherence was higher but still suboptimal.