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In a series of studies, Finnish researchers confirmed that those traveling to exotic locations—places with poor hygiene and free-flowing antibiotics—often bring home drug-resistant bacteria in their intestines (with or without symptoms). But the people who took antibiotics while exploring those locales came back with the most extensively drug-resistant cargo.

The findings, published in the journal Travel Medicine and Infectious Disease, suggest that taking antibiotics while abroad may be far more dangerous than most travelers know. After all, it’s common for world explorers to preemptively pack antibiotics, such as ciprofloxacin, for common ailments, like travelers diarrhea, the authors note.