BALTIMORE (WJZ) — A health warning. The extremely contagious measles virus is back. An outbreak that started at Disneyland is starting to sweep the country.

Christie Ileto has the push for children to get vaccinated.

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Measles was thought to have been eliminated in the U.S. 15 years ago. Now its back, targeting those who haven’t been immunized.

The outbreak that started in California’s Disneyland is expanding. At least 75 cases of measles span six states.

“It’s scary to think the happiest place on Earth is infected with measles,” one Disney employee said.

For this Disney employee, knowing co-workers are infected is cause for concern.

Measles has a 21-day incubation period, meaning people  can travel far before they know they’re sick.

“We’re seeing the resurgence of measles because a lot of the parents are not getting their children vaccinated,” said Dr. Peter Andrews, Sinai Hospital.

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Dr. Andrews says that problem is prime. In Maryland, all students K-12 must get two shots of the measles vaccine.

“It just didn’t make sense to me,” said one Annapolis mom.

In a revealing interview with WJZ, an Annapolis mom explained why she didn’t vaccinate her kids.

“I didn’t understand why a little human had to get so many drugs at one time,” she said.

Still, the vaccine proves very effective if given at two doses.

Doctors say the virus is highly contagious. For instance, if someone has the measles and doesn’t cover their mouth when they sneeze, they can pass it on to anyone standing nearby.

Symptoms like fever, cough and rash soon follow.

“The younger, the older, the immune compromised. Those are the three target areas that really can get sick and die,” said Dr. Andrews.

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Most people who have already had the measles or got the vaccine are not at risk.