– A measles outbreak that began at Disneyland prompted warnings about potential exposure at theme parks and airports, and reawakened concerns that an anti-vaccination movement may help fuel the spread of the disease.

New infections linked to the theme parks emerged in the outbreak that has spread to five U.S. states and Mexico, though the vast majority — 62 of the 70 cases — occurred in California.

People who have not received the measles-mumps-rubella, or MMR, vaccine are susceptible to contracting the highly contagious illness and should avoid Disney "for the time being," state epidemiologist Gil Chavez said.

The same holds true for crowded places with a high concentration of international travelers, such as airports, Chavez said. People who are vaccinated don't need to take such precautions, he said.

Disneyland Resorts spokeswoman Suzi Brown said officials agreed with the advice that "it's absolutely safe to visit if you're vaccinated."

Of the confirmed cases of measles in California since December, 42 have been linked to an initial exposure at Disneyland, including five employees, according to the state's Department of Public Health.

In Orange County, where the theme park is located, the school district may bar students who aren't vaccinated and may have been exposed.

"The best way to prevent measles and its spread is to get vaccinated," Ron Chapman, director of the California Department of Public Health, said in a statement Wednesday.

Of the 34 measles patients whose medical histories are known, 28 were unvaccinated, the health department said. An increasing number of parents are choosing not to vaccinate their children or delay their shots, citing concerns about other health risks, with large numbers of underimmunized children appearing in some California communities.

Measles is a highly contagious, airborne disease. Victims develop a fever, runny nose and a rash. About one in 20 children with measles catch pneumonia and a small number develop encephalitis, according to the Centers for Disease Control and Prevention. In some cases it is fatal.

The disease has been largely eliminated in the United States, although it is occasionally brought into the country by tourists or Americans who catch it abroad. In 2014, there were 644 cases amid 23 outbreaks, the most since at least 2000, the CDC said.

Resistance to vaccination is more prevalent in some communities. A study of 154,424 children covered by Kaiser Permanente in Northern California found five geographic clusters where children were significantly more likely to be underimmunized by their third birthday, including almost 1 in 4 toddlers in part of Vallejo, a city in the San Francisco Bay Area.

The number of children who aren't getting the recommended vaccines, or receiving them on time, is on the rise, said the study, published in the journal Pediatrics.

The Associated Press contributed to this report.