The U.S. Centers for Disease Control and Prevention (CDC) is cautioning travelers going to Mexico to stay up to date on their vaccinations and to look out for signs of illness amid an outbreak of hepatitis A virus (HAV), Travel Pulse reports.

According to the CDC, as of May 1 more than two dozen hep A cases have been reported among U.S. visitors to Tulum, a popular tourism destination in eastern Mexico that is famous for its Mayan ruins. Travelers who ate or drank there between February 15 and March 20 of this year are now being advised to look out for symptoms.

The CDC is also advising prospective travelers to get vaccinated for HAV in advance, and to make sure they are consuming safe foods and beverages and maintaining good hygiene practices while abroad.

Currently, the CDC warning for Tulum is only set at Level 1, which urges “usual precautions” for avoiding illness. Only the highest warning, Level 3, would advise travelers to avoid the region completely.