Novel app enables surveillance of global travel-related illness

On around one in three trips someone falls ill, with gastrointestinal and respiratory complaints among the most common symptoms. These are the findings of a new study based on data from a travel app developed by researchers at the University of Zurich. The app could be used in the future to help detect outbreaks of contagious diseases at an early stage.

Travelers sometimes pick up more than just memories when they go abroad. Unfortunately, they may also experience health issues brought about by pathogens. Data collected by a novel travel app developed by UZH researchers in cooperation with the World Health Organization (WHO) now shows that this happens remarkably often. The app is not only useful for travelers but may also help track outbreaks and the spread of infectious diseases such as dengue or novel influenza viruses.

Travelers are an excellent reflection of what's happening around the globe. They also often play a part in introducing pathogens to different regions of the world."

Patricia Schlagenhauf, study leader, from the Epidemiology, Biostatistics and Prevention Institute at UZH

By way of example, she cites the recent case of mpox in Sweden, which was imported by a traveler returning from Africa.

Tracking the spread of infections

The Illness Tracking in Travellers (ITIT) app lets people who are on the move report daily symptoms by filling in a short, user-friendly questionnaire. This information is then linked to location data as well as climate and air quality information. The research team has now analyzed data collected through the app between April 2022 and July 2023. The analysis covered 470 trips recorded by 609 people across all continents. Travelers fell ill surprisingly often during their travels, with health issues occurring on more than one-third of trips.

Gastrointestinal symptoms top the list

The most common health issues were gastrointestinal symptoms, which were reported in 19% of trips and most frequently in travelers to Asia. In contrast, these symptoms occurred less often in people traveling to Africa. Significantly more women than men reported symptoms of diarrhea. It is possible that women are more susceptible to diarrhea, or that they were more conscientious when recording symptom information in the app.

By contrast, respiratory diseases (17%) such as colds were most common among travelers in Europe. "Don't forget that you should carry a first-aid kit even when you're traveling to supposedly low-risk countries like France or Greece," says Schlagenhauf. She recommends that travelers pack medication to treat diarrhea, nausea, headache and fever, since these are the health issues that people are most restricted by on their travels, according to the study.

Healthy and safe travels

The research team would now like to invite even more people to use the app. Larger sets of data would enable the researchers to run automated analyses using artificial intelligence, which could, for example, be used to detect outbreaks of dengue or mpox at an early stage.

"This real-time bottom-up approach is much faster than top-down reporting systems," says Schlagenhauf. Even in well-organized government bodies such as the Swiss Federal Office of Public Health, it often takes months for case numbers to be available. "Mobile technologies offer a revolutionary solution to how we track travel-related illnesses. This will ultimately make our travels safer and healthier."