Measles cases in the U.S. are at the second-highest level in 25 years, with the number expected to rise. There have been 555 reported measles cases in 2019 as of last Thursday, according to figures the Centers for Disease Control and Prevention released Monday. That’s 183 cases more than last year, and only 112 cases fewer than in 2014, when there were 667 cases. Since it’s only April, this year’s number is likely to surpass 2014′s and could rival the 963 cases in 1994, 25 years ago. As of last week, the CDC said the disease has spread to five more states ― Florida, Indiana, Maryland, Massachusetts and Nevada ― bringing the total number of states affected up to 20.

CDC From Jan. 1 to April 11 this year, there have been 555 individual cases of measles confirmed in 20 states. This is the second-greatest number of cases reported in the U.S. since 1994.

Arizona, California, Colorado, Connecticut, Florida, Georgia, Illinois, Indiana, Kentucky, Maryland, Massachusetts, Michigan, Missouri, Nevada, New Hampshire, New Jersey, New York, Oregon, Texas and Washington have reported measles cases. “I’m obviously very concerned about the size and also acceleration of the current outbreak,” Dr. Nancy Messonier, director of the CDC’s National Center for Immunization and Respiratory Diseases, told CNN. “This is not going to stop on its own.” Measles is on the rise globally, with 300% more reported cases in the first three months of 2019 than in the same period last year, the World Health Organization said on Monday.

Preliminary global data on #measles shows that reported cases rose by 300% in the first three months of 2019, compared to the same period in 2018. This follows consecutive increases over the past two years. https://t.co/fY27Rlzlqw#VaccinesWorkpic.twitter.com/oImdYl4L9G — World Health Organization (WHO) (@WHO) April 15, 2019

There are currently outbreaks in the Democratic Republic of Congo, Ethiopia, Georgia, Kazakhstan, Kyrgyzstan, Madagascar, Myanmar, the Philippines, Sudan, Thailand and Ukraine. The outbreak in Madagascar, the largest in the country’s history, has killed more than 1,200 people, most of them children, The Associated Press recently reported. Officials attribute the high number of deaths to low vaccination rates, poverty and malnutrition. “In 2017, the most recent year for which estimates are available, it caused close to 110,000 deaths,” the WHO said in a release. “Even in high-income countries, complications result in hospitalization in up to a quarter of cases, and can lead to lifelong disability, from brain damage and blindness to hearing loss.”

ASSOCIATED PRESS A volunteer nurse at a health care center in Larintsena, Madagascar, examines a 6-month-old who has measles while her mother, Nifaliana Razaijafisoa, looks on.

Measles was nearly eliminated in the U.S. in 2000. The CDC attributes the rise of measles cases in the country to outbreaks in unvaccinated communities after travelers overseas contracted the disease and brought it to the U.S. Last year, 82 people brought measles to the U.S. from other countries. It was the greatest number of imported cases since 2000. Health officials have urged the public to get vaccinated for the disease, as the majority of people who have contracted measles were unvaccinated. New York City Mayor Bill de Blasio declared a public health emergency last week that would require vaccinations for people living in Williamsburg, Brooklyn, where parents in ultra-Orthodox communities oppose vaccinating their children.

Shannon Stapleton / Reuters A sign in Williamsburg warning people of measles two days after New York City Mayor Bill de Blasio declared a public health emergency in parts of Brooklyn.