Expect even more measles outbreaks in the United States in coming years, public health experts say, thanks to overseas epidemics and growing misinformation efforts by anti-vaccination activists.

Outbreaks of the highly contagious virus are now active in 20 states, with 555 confirmed cases in the US this year alone, according to the CDC. That’s well on track to exceed 2014’s record of 667 cases, the highest number recorded since the disease was declared domestically eradicated in 2000.

All of the new US outbreaks originally derived from infections transmitted by travelers — either visitors from overseas, or US residents who went abroad. “Every case we have now is associated with travel,” Thomas Clark, deputy director of the CDC's viral diseases division, told BuzzFeed News. And with measles cases now surging outside of the US too — seeing a 300% global increase this year compared to last — we are likely to see more cases here, public health experts say.

“It is unfortunately the new normal,” Harvard Medical School epidemiologist John Brownstein told BuzzFeed News. And the booming anti-vaccine movement in the US and across the world is making it harder to keep it in check, he said.

On Monday, the World Health Organization reported that 170 countries have confirmed more than 112,000 cases so far in 2019. That’s probably an underestimate, as only about 1 in 10 actual cases is reported to the WHO. Severe outbreaks in countries such as Madagascar, the Philippines, and Ukraine, among others, are, “causing many deaths — mostly among young children,” according to the health agency. Those epidemics are leading to outbreaks even in countries with good overall vaccination rates, such as Israel, Thailand, and the US.

“Absolutely what we are seeing is that under-vaccinated areas in the US are the kindling and the huge numbers of infections overseas are the spark that ignites outbreaks here,” Baylor College of Medicine infectious disease expert Peter Hotez told BuzzFeed News.

Measles is largely preventable by vaccination, which stops transmission of the disease after a second dose in 97% of cases and lessens its severity in rare cases that slip through. But the virus is highly contagious: If exposed to someone with the virus, 9 out of 10 unvaccinated people will get sick themselves. That means communities need to have a high rate of overall vaccination, around 95%, to provide “herd immunity" to the disease.

About half of the US outbreaks have happened in close-knit religious or ethnic communities, said Clark, “that can be insular or, for whatever reason, resistant to vaccination.”

The biggest US outbreak, nearly 300 reported cases in New York City, has largely struck the ultra-Orthodox Jewish community in Brooklyn, for example, and traces to an outbreak in Israel. That Brooklyn community and another Jewish group in Rockland County, New York, where 180 cases have been reported, were targeted by anti-vaccination propaganda efforts, according to local public health officials, another growing factor in the outbreaks.