A study shows how international travel affects the gut microbiota

• Although travel has clear benefits, it can also be an important factor in the spread of infectious diseases

• A diverse and resilient microbiota is key to good health, and understanding how travel affects it could help design better preventative strategies

Globalization has allowed countries and people to be more interconnected than ever before. The improvement of transport infrastructure, together with the relaxation of visa policies, has made moving between countries more accessible, and proof of this is the great increase in international travel in recent decades. Last year more than 1.300 billion people traveled abroad, and the figure this 2024, according to UN estimates, is on its way to surpassing it.

Although travel has clear benefits – such as cultural exchange, business and tourism – it can also be an important factor in the spread of infectious diseases, as microorganisms move to new geographical areas. This cause-and-effect relationship was clearly seen with the COVID-19 pandemic and is likely to remain an issue in the future.

One of the most common health problems among tourists is what is known as 'traveler's diarrhea', which is linked to the colonization and subsequent transmission of bacteria resistant to antimicrobials such as antibiotics. Although the colonization of these bacteria can be transient and disappear once you return to the country of origin, they can spread quickly and contribute to the increase of antimicrobial resistance.

Recent studies suggest that the state of the intestinal microbiota – which are the microorganisms that live in our gastrointestinal tract – plays an important role in the propensity for this diarrhea and colonization by bacteria with antibiotic resistance during travel. Specifically, it has been observed that a lack of diversity in the gut microbiota is associated with disease, while a healthy and diverse microbiota is linked to better health.

In relation to these observations, the community and health care-related infections research group from the Parc Taulí Research and Innovation Institute (I3PT) has participated in a study with the Sant Joan de Déu Research Institute (IRSJD) to determine if traveling and exposure to new people, traditions, cultures and unfamiliar foods can change the gut microbiota and its diversity.

To do this, two prospective groups were analyzed. The first was a group that included travelers who planned to go abroad for more than three months. These participants provided faecal samples before and after their international travels in order to assess possible changes in the microbiota. The second group consisted of travelers who had returned the previous month after a long stay in a non-European country, migrants from non-European countries and a group of individuals who had not traveled in the previous year. All of these participants provided a single fecal sample, and the gut microbiota of those who had traveled was compared to that of those who had not.

In the first group, a trend towards greater bacterial diversity was observed after the trip. In the second group, after comparing travelers/migrants with non-travelers, a greater diversity in the microbiota of the former was confirmed, especially in those travelers from less industrialized rural areas. Thus, the study shows that international travel influences the composition of the gut microbiota and that this impact may vary depending on the traveler's epidemiological history, destination, and underlying health conditions. “This is important because A diverse and resilient microbiota is key to good health, and understanding how travel affects it could help design better preventative strategies, such as the use of probiotics or changes in the diet to promote a healthy microbiota before and after travelling", concludes Monsálvez.