Five more people who visited Disney theme parks in California last month have fallen ill with measles, bringing the number of cases in the state to a dozen, local health officials said Friday.

Six patients in Southern California’s Orange County have been diagnosed with the illness who visited the local theme parks last month, and only one was fully vaccinated against the disease, said Nicole Stanfield, a spokeswoman for the county’s health care agency.

More people may have been exposed when measles patients were treated at two local hospitals and a lab, county officials said. Stanfield urged anyone with measles symptoms to call their doctor before seeking medical attention to avoid exposing others to the highly contagious illness.

“The medical provider may visit them in the car or may have a special room for them to go where they’re not contaminating everyone else in the waiting room,” she said.

California’s health care agency has reported seven people in the state and two people in Utah likely contracted measles on trips to Disneyland or Disney California Adventure between Dec. 15 and Dec. 20. In Colorado, the El Paso County Public Health department said a patient was diagnosed with measles at a Colorado Springs hospital after visiting a California theme park.

Disney officials have said they are working with public health authorities to provide any necessary assistance.

Measles is a highly contagious virus that lives in an infected person’s nose and throat mucus and spreads through coughing and sneezing, according to the federal Centers for Disease Control and Prevention. Symptoms include fever, cough, runny nose and red eyes and a red rash that usually first appears on the face and spreads to the rest of the body.

Health experts say the best prevention against measles is vaccination. While officials declared measles eliminated in the United States in 2000 because of a lack of continuous transmission, the illness is still brought into the country by foreign visitors or unvaccinated Americans.

Tags: disney, health
Photo Credit: Balloons of Mickey Mouse are carried down main street at Disneyland in Anaheim, California, March 11, 2011. Mike Blake / Reuters