A measles outbreak traced to Disney theme parks in California led to warnings against visiting the happiest place on Earth if tourists or their children have not been vaccinated against the highly contagious respiratory disease that has sickened 70 people.

New infections linked to the theme parks emerged Wednesday in the outbreak that has spread to five U.S. states and Mexico, though the vast majority — 62 — 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."

The people who have been infected range in age from 7 months to 70 years old. The vast majority had not been vaccinated, and a quarter had to be hospitalized.

Among those sickened were five Disney employees, three of whom have since returned to work. The company previously said park employees who may have been in contact with infected people were asked to show proof of vaccination or have a blood test to show immunity against measles. Those with pending results were put on paid leave. Vaccinations are also being offered to all employees.

Measles has hit California hard recently, where four to 60 measles cases a year are typical.

"We are off to a bad start in 2015," Chavez said.

Since the outbreak, two dozen unvaccinated students at an Orange County high school were sent home for three weeks after an infected student showed up.

Eradicted since 2000

Measles can spread by air through coughing or sneezing. Symptoms include fever followed by cough, runny nose and a blotchy rash. Though the virus has been eradicated in the U.S. since 2000, it can still enter the country through an infected traveler.

While health officials said they likely may never find "patient zero," or the trigger of the outbreak, they believe it was either a resident from a country where measles is widespread or a Californian who went abroad and brought home the virus.

People at highest risk are those who are unvaccinated, pregnant women, infants under 6 months old, and those with weakened immune systems.

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