More than 34,000 Europeans were infected with the measles during the first two months of 2019, most of whom are in Ukraine but who inhabit 42 countries in all. In a new report, the World Health Organization warns vulnerable people to get vaccinated — especially if they plan on traveling.

Experts expect the outbreaks to spread if the “response is not timely and comprehensive.”

Measles diagnoses have reached more than 25,000 in Ukraine alone and the disease has killed 13 total among there, Romania and Albania. Outbreaks have also been identified in Thailand, the Philippines and the US.

“Every opportunity should be used to vaccinate susceptible children, adolescents and adults,” said WHO officials, noting that a vast majority of these cases are in unvaccinated people.

In 2017, the European region reached its highest-ever measles vaccination rate at around 90 percent, but experts agree that herd immunity — which describes sufficient disease resistance in a community — for the measles should be closer to 95 percent to achieve relative eradication of the virus. Over the past three years, some countries have lagged in immunization among marginalized and vulnerable groups.

Last month, the United Nations children’s fund released a report revealing that every year, more than 20 million children have missed their measles vaccine for the last eight years.

Measles can cause blindness, deafness or brain damage, and has no known cure, but can be prevented with two doses of the vaccine.

“The impact on public health will persist until the ongoing outbreaks are controlled,” the report read, pushing local authorities to “identify who has been missed in the past and reach them with the vaccines they need” as soon as possible.