The Atlanta-based U.S. Centers for Disease Control and Prevention is warning summer vacationers to beware of measles if they plan to travel to Europe.

Outbreaks in Europe over the past year have caused the deaths of 35 people. More than 14,000 have been infected. Fifteen European countries have reported cases in 2017.

The CDC has issued travel notices for five countries, most recently France. The worst-hit country by far is Romania, with 31 deaths, according to the World Health Organization.

The most recent known death is of a 6-year-old boy in Italy. He caught it from an unvaccinated older sibling, according to news reports. As in the United States, misinformation about the measles vaccine has led to some Italian parents refusing vaccination for their children, which can both endanger those children and make them carriers who put other children in danger.

The CDC's advice for travelers this summer is to be vaccinated against measles, and to practice clean hygiene.

"Every death or disability caused by this vaccine-preventable disease is an unacceptable tragedy," Dr. Zsuzsanna Jakab, the WHO regional director for Europe, said in a statement.

“We are very concerned that although a safe, effective and affordable vaccine is available, measles remains a leading cause of death among children worldwide, and unfortunately Europe is not spared.”