California health officials on Thursday confirmed 13 new measles cases connected to an outbreak at Disney theme parks last month, bringing the total number of illnesses to 39.

The new cases of the airborne illness include five in Los Angeles County and one in San Diego County.

The San Diego County cases include at least five people who showed up with fevers and rashes Wednesday at the Sharp-Rees-Steely Urgent Care Clinic in the suburb of La Mesa.

The clinic was shut down for several hours and dozens of other patients at the clinic were questioned about their medical histories, officials said.

Craig Sturak with the San Diego County Health and Human Services Agency said Thursday that the public may have been exposed at that clinic and eight other places including drugstores, grocery stores and gyms.

Officials said 35 of the confirmed cases are in California, two are in Utah and one apiece in Colorado and Washington.

Many were not vaccinated against the disease.

Of the 10 total cases in San Diego, only one patient had been vaccinated, Sturak said. Exact figures were not immediately available for other areas.

Most of the patients visited Disneyland or Disney California Adventure between Dec. 15 and Dec. 20, but some contracted the illness from others who visited.

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 U.S. in 2000 because of a lack of continuous transmission, the illness is still brought into the country by foreign visitors or unvaccinated Americans.