More and more tourists are bringing home more than souvenirs. They're picking up the hepatitis A virus during their travels.

About 10 million people in the world pick up the infection every year, according to estimates. "And the numbers are climbing, because ever more people are traveling," says Anton Gillessen, chief doctor for the internal medicine clinic at the Heart of Jesus hospital in Muenster, in Germany.

Anyone traveling to southern or eastern Europe, the Mediterranean region (including Greece, Egypt or Tunisia) or any tropical region should consider an immunization before travel, recommends the Robert Koch Institute in Berlin. That's because 40 to 50 percent of all infected people catch the infection while on vacation.