Minnesota is grappling with 73 cases of measles right now — more cases than the entire country had last year. The outbreak is thanks to people who don’t vaccinate their children, according to the Minnesota Department of Health. These people wrongly believe a debunked theory that vaccination causes autism.

The Minnesota outbreak has exposed more than 8,000 people to the virus, mostly in schools and hospitals. “Many of the cases could have been prevented if people had gotten vaccinated," Kristen Ehresmann, director of the Infectious Disease Epidemiology, Prevention, and Control Division at Minnesota’s Department of Health told CNN. When fewer and fewer people are vaccinated, it puts everyone else at risk, too — especially those who aren’t vaccinated because they’re too young or sick.

Measles is a viral infection that causes high fever, a red rash, and, in more serious cases, blindness or brain inflammation. It’s highly contagious and can be spread through the air. Two doses of the MMR vaccine that protects against measles, mumps, and rubella is about 97 percent effective in getting rid of the disease, but that’s not much use if people aren’t being vaccinated. Measles was once declared eradicated from the United States, but it has since made a comeback. Last year alone, there were 70 measles cases in the country.

A National Institutes of Health study last year confirmed that growing fears of vaccination were partly to blame for the resurgence of measles. This is especially true among the region’s Somali community. In Minneapolis, fewer than half of Minnesota children of Somali descent have received the MMR shot because their parents believe it causes autism, according to NPR.

"It is a highly concentrated number of unvaccinated people," Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy, told NPR. "It is a potential kind of gas-and-match situation."