California public health officials are responding to an ongoing outbreak of measles with widespread outreach efforts, urging people to get vaccinated against the preventable but highly contagious disease.

There were six confirmed cases in Alameda County and 79 in California as of Wednesday, according to the California Department of Public Health’s website. The majority of those infected are “epidemiologically connected” to Disneyland or Disney California Adventure Park, where the outbreak began in December.

“We have a very effective and very safe vaccine,” said Dr. Janet Berreman, Berkeley’s health officer. “There’s no shortage of the vaccine, and there’s plenty of it available for people who want it.”

Fever, cough, runny nose and red eyes typically precede a skin rash, a key symptom of measles. Particles of the virus can remain in the air for up to two hours after an infected person coughs, and people are often contagious before their symptoms appear.

But two doses of the measles, mumps and rubella vaccine are 99 percent effective in preventing the virus.

Measles was eradicated in the United States as of 2000, so most novel cases originate from international travelers and then spread to unvaccinated people.

“We’re working with all schools (in Berkeley) to make sure the principals and administrators understand what the impacts are of getting kids vaccinated,” said city spokesperson Matthai Chakko.

Health care providers have to report cases of measles to the local public health department, according to Berreman.

Public health workers then contact the infected individual to discuss where the person went and with whom they came into contact, which Berreman said is one of the most effective ways to prevent the spread of the virus.

Sometimes it is impossible to reach out to everyone that a sick person came close to, as with the two UC Berkeley students who rode BART and attended classes last spring while infected with measles. In response to those cases, BART issued a news release detailing how to recognize symptoms, according to BART spokesperson Taylor Huckaby.

Children under 1 year of age and people with certain allergies and illnesses cannot get vaccinated, but according to Arthur Reingold, professor and head of epidemiology at the UC Berkeley School of Public Health, the number of people opting out of inoculation has grown substantially in states where exempting oneself is easy. California changed its laws in January 2014 to make this a more difficult process.

Certain communities in California, including Marin County and parts of the East Bay, have higher rates of nonimmunization, Reingold noted. If a case appears in a school, administrators sometimes exclude children until they get vaccinated.

“Parents have had more fear of the vaccine than the disease,” Reingold said. “We really think the appropriate amount of (measles) cases in U.S. is zero.”