Real-time illness monitoring in travellers: an international, prospective, digital surveillance study

International travel is growing exponentially. Monitoring infectious disease in travellers is increasingly important to identify infection trends and signals. The ITIT (illness Tracking in Travellers) app project aims to monitor travel-related illness in a prospective, real-time surveillance study (ClinicalTrials.gov NCT04672577) integrating geolocation and environmental data.

Adults (>18 years) traveling internationally (>2 days), provided e-consent and used the ITIT app to record daily illness symptoms, which were analysed together with geospatial and climate data. All data are encrypted. A pre-travel survey collected demographic and itinerary data and follow-up surveys assessed post-travel diagnoses and self-treatment.

1355 participants enrolled until December 2024; 676 completed symptom surveys covering 703 trips. Symptoms were reported in 42 % of trips, with gastrointestinal, respiratory and general symptoms being the most common. Post-travel diagnoses were reported in 6 % of respondents, including malaria, COVID-19, and schistosomiasis. Self-treatment was reported by 20 % of travellers. Participants visited 95 countries and reported symptoms in 70. The most common destinations of travel with symptoms reported were Indonesia, Thailand and Pakistan. Duration of travel and the age of the traveller were the most important demographic factors for predicting symptom occurrence.

ITIT enables real-time global health surveillance in travellers and can augment traditional surveillance systems, particularly in regions with limited infrastructure.