The California measles outbreak has resulted in 70 cases, crossed five state lines and one international border, and it could continue to spread, according to the latest update from the California Department of Public Health. Several people who were vaccinated also have fallen ill with the highly contagious viral infection. Health officials have warned that the epidemic, whose origin was linked to a handful of cases from Disneyland in Anaheim, could get worse.

"We can expect to see many cases of this vaccine-preventable disease unless people take precautionary measures," Gil Chavez, state epidemiologist and deputy director of the Center for Infectious Diseases, told reporters Thursday. "People who are unvaccinated should know that there is presently a risk for getting measles in California.”

Of the confirmed cases, 62 were in California, three were in Utah, two in Washington state, one in Colorado, one in Oregon and one in Mexico. Forty-two have been traced back to Disneyland, including five Disney employees. The first infections were detected in December. Health officials have told people who have not been immunized to steer clear of the parks as well as airports, malls and tourist destinations where international travelers could congregate, as officials believe the first case may have come from overseas.

As officials work to contain the outbreak, health experts and vaccination skeptics debate whether it's the result of the increasing anti-vaccination campaign that has led to a growing number of parents – often from wealthier communities – not vaccinating their kids. Parents often cite health concerns as their reason for not vaccinating, but health officials have said those fears are unfounded.

Polls have shown that one in three Americans still believe vaccinations may cause autism, despite the research having been widely condemned as false. “Vaccines are under so much more scrutiny than other medical products because they’re given to healthy people,” Amy Pisani, executive director of Every Child by Two, an advocacy group for public vaccine education, told International Business Times. “There’s so much that goes on behind the scenes to make sure they stay safe.”

Despite the assurance from health experts that vaccines are safe, five of the people infected during the current measles outbreak actually had been immunized. Health experts said that even the vaccinated have a small risk of getting sick, especially if the vaccination was received 50, 40 or 30 years ago when federal guidelines required people to get only one shot, the Los Angeles Times reported.