SANTA ANA, Calif. — Struggling to contain a growing measles outbreak that started at Disneyland a month ago, Orange County health officials ordered about two dozen high school students without proof of immunization to stay away from campus.

The move came as officials confirmed five Disneyland employees were diagnosed with the measles, part of what officials described as the worst outbreak in California in 15 years. There are now a total of 54 patients across California as well as three other states and Mexico.

Health officials ordered the students out of class after they learned that a Huntington Beach High School student who was infected with the disease had come to class when school resumed in January. They said they would take the same action in other schools if measles are detected.

“If there is a case in the school and their child is not immunized, they will be removed from the school for 21 days,” said Dr. Eric Handler, the Orange County public health officer.

“From an epidemiological standpoint, in order to prevent spread of the disease, this is a necessary measure.”

Orange County is home to several upscale communities where a higher than average number of parents have opted to not fully vaccinate their children because of their personal beliefs.

Experts say it’s a problem when 8 percent or more decline vaccines that keep diseases such as measles from spreading.