If you or someone in your family hasn’t received a measles vaccine, you should strongly consider staying away from Disneyland. California public health officials say the park has been linked to a recent outbreak of the disease, and they are urging people who have not been inoculated to keep their distance.

California has been dealing with an outbreak of measles since December, and a large majority of the 59 people who have contracted the disease got it at Disneyland. According to health officials, 42 people, including five of the park’s employees, caught measles at the Southern California theme park.

State health officials have taken aggressive steps to contain the spread of the disease. Twenty-four classmates of one high school-aged patient were ordered to stay home for three weeks, the disease’s incubation period.

Yet measles is highly contagious, and the same outbreak has been cited as the cause of five cases that recently turned up in Oregon, as well as cases in three other U.S. states and Mexico.

Though nearly 95 percent of U.S. children are vaccinated against measles, there are a number of communities dotted across the country where parents have chosen not to vaccinate them. Gil Chavez, the deputy director of the California Department of Public Health, says there are some schools in California where as many as 30 percent of the attending children have not received the correct vaccinations.

“That’s a powder keg waiting for a match,” Chavez told USA Today.

Though measles has effectively been eradicated in the United States, it remains relatively common in many parts of the world, and foreign visitors will periodically cause brief outbreaks here. According to the Center for Disease Control, a recent outbreak in the Philippines contributed to the majority of measles cases in the United States last year.

The origins of the California outbreak have not yet been determined.