The outbreak, the largest in the Golden State in more than 20 years, also may have infected dozens of residents visiting Disneyland or Disney California Adventure Park in Anaheim from other states and countries, officials said.
Of the more than 130 cases of the disease confirmed in the state since January, 40 had recently visited one or both of the parks.
Seventeen of the cases were in the San Francisco Bay Area.
While the exact source of the disease has not been identified, health officials blamed the outbreak on falling vaccination rates among children and adults, according to the San Francisco Chronicle newspaper.
“Vaccination rates need to be higher in some communities,” Dr. Gil Chavez of the California Department of Public Health told reporters Friday on a conference call.
“I believe that because we have these pockets of high non-immunization that we are susceptible to these types of outbreaks,” he said.
Measles is highly infectious and characterized by a red rash that usually appears first on the face and then spreads downward over the rest of the body.
Infection usually begins with fever, cough and red eyes, health officials said.
Nineteen percent of the people who contracted the disease this year had to be hospitalized, and two had to be hospitalized for three or four weeks and hooked to ventilators.
But all of them have recovered or are nearly recovered, the newspaper said.
State medical authorities have declared the outbreak over because more than 42 days have passed since the last confirmed infection, the newspaper said.
The last confirmed case in California was reported on March 2.
“We are confident if we had higher levels of vaccination this outbreak would not have happened,” Chavez said.
California allows parents to refuse to vaccinate their children if it would violate their “personal beliefs.”
But the 2015 outbreak has forced the state to rethink the advisability of that exemption, particularly because the measles vaccine is considered extremely safe and effective.
“We have a vaccine that is very effective,” Chavez said. “These complications should not occur in this day and age.”
Now, a new proposal pending in the California legislature would require children to be vaccinated before starting kindergarten, the newspaper said.
But the disease outbreak also appears to have rekindled public debate on whether the state should require immunization at all or leave such decisions to families.
At a recent hearing on the bill before the state Senate Education Committee, hundreds of parents denounced the proposal and threatened to keep their children out of school rather than get them vaccinated, the newspaper said.
Some 90 percent of California schoolchildren are fully immunized when they start kindergarten but rates vary in different parts of the state and in certain schools, official said.
In affluent Marin County, for example, only 84 percent of children are immunized and less than half of kids are fully vaccinated in some schools.
