The nation’s health agency on Monday warned doctors about an increase in measles cases that in a little more than three months has equalled all of the U.S. cases from last year.

There were 58 confirmed cases of measles in the U.S. this year as of Thursday, the Centers for Disease Control and Prevention said, compared to 58 in all of 2023.

In the cases this year, 93% were linked to international travel, the agency said. Most of the cases involved children a year or older who haven’t yet gotten a measles-mumps-rubella vaccine, or MMR.

“Healthcare providers should ensure children are current on routine immunizations, including MMR,” the agency said in an advisory to medical providers.

Seventeen states have reported cases this year. In New York, the cases were reported in New York City, the CDC says on its website.

There are also outbreaks in other countries, including Austria and the United Kingdom, so anyone of any age traveling to any international destination should be current on their vaccinations, the agency said in the advisory.

Measles is highly contagious and unvaccinated people have a 90% chance of becoming infected if exposed.

Late last month there was a large outbreak in Florida, and in January there was one in Philadelphia.

It can also be fatal. In 2021, an estimated 128,000 people, most of whom were children, died from the disease, the World Health Organization organization says.

It estimates that 56 million deaths were averted by vaccination worldwide between 2000 and 2021.

Measles was declared eliminated in the U.S. in 2000, which means no continuous disease transmission for greater than 12 months, or not constantly present in the country, according to the agency.

The U.S. retains its eliminated status, but in 2019 there was a 27-year high with 1,274 cases. Those outbreaks were all travel-related cases that then infected people who are unvaccinated or under-vaccinated in the U.S., the CDC has said.