Disneyland measles outbreak spreads to Bay Area

Fans attend a Disneyland event in 2013. A large outbreak of measles that started at two adjacent Disney theme parks in December has now sickened people all over California. Fans attend a Disneyland event in 2013. A large outbreak of measles that started at two adjacent Disney theme parks in December has now sickened people all over California. Photo: Mindy Schauer / Associated Press Photo: Mindy Schauer / Associated Press Image 1 of / 4 Caption Close Disneyland measles outbreak spreads to Bay Area 1 / 4 Back to Gallery

A large outbreak of measles that started at two adjacent Disney theme parks in December has now sickened people all over California, including a handful of Bay Area residents, and is prompting public health authorities to urge everyone to get vaccinated if they aren’t already.

California has reported 59 cases of measles since mid-December, the bulk of them in people who either visited or had close contact with someone who had been to Disneyland or California Adventure Park in Anaheim, public health officials said in a media conference call Wednesday. Seven measles cases have been reported in the Bay Area: in Alameda, San Mateo and Santa Clara counties.

Most of the people who have become infected were unvaccinated. Because of the threat of infection, public health officials said people who aren’t vaccinated — either because they can’t get the vaccine or they choose not to — should avoid public places where large groups of people, especially international travelers who may carry measles, congregate.

“We can expect to see many more cases of this vaccine-preventable disease unless people take precautionary measures,” said Dr. Gil Chavez, deputy director of the Center for Infectious Diseases with the California Department of Public Health. “I am asking unvaccinated Californians to consider getting immunized to protect themselves and family and community at large.”

Measles is considered eradicated in the United States. Before the vaccine was developed in the 1960s, California would see up to 40,000 cases a year. That number has dropped steadily since then. In the past two decades, with more than 90 percent of children vaccinated, cases have ranged from a low of four in 2005 to 60 in a year with a large outbreak.

The current outbreak is unusually large, and public health officials said they expect to see many more cases in the coming weeks.

Measles is caused by a highly contagious virus that can remain airborne and capable of infecting people for hours. Measles can cause serious illness, including death. One-quarter of those infected in the current outbreak have been hospitalized.

Symptoms of measles

Initial symptoms include high fever, runny nose and watery eyes, which often are mistaken for influenza or a bad cold before the more obvious symptoms of measles — a rash and red eyes — set in. That means many cases often go undiagnosed for several days while people walk around and potentially expose others.

Last February, a Contra Costa County resident sick with measles took BART to commute to classes at UC Berkeley, prompting an aggressive public health campaign to reach the tens of thousands of people who may have been exposed. Public health officials believe that the student, who was not vaccinated, contracted measles during a visit to the Philippines.

In the current outbreak, Alameda County public health authorities have talked to more than 500 people who may have had contact with one of the five people diagnosed with measles, said spokeswoman Sherri Willis.

Cases reported in the United States are almost always linked to unvaccinated residents who contract the illness overseas and bring it home, or from international travelers who carry measles into the country. Public health officials said they don’t know who sparked the Disney-related outbreak, but it was almost definitely someone who had been out of the country.

Video: Measles outbreak linked to Disneyland

The measles vaccine prevents infection in 99 percent of people. Generally children get two doses of the vaccine, one at age 12 to 15 months and a second before starting kindergarten.

Of the 59 cases reported in the state so far, public health officials were able to get the vaccination status of 34 people — 28 of them had not been vaccinated, including six infants who were too young to get the first shot.

Increasing numbers of California schoolchildren are not being fully vaccinated. The rate of parents filing “personal belief exemptions” to allow their children into school without being fully immunized has doubled since 2007, according to the state public health department.

Pockets of communities have especially large rates of under-vaccinated children, according to a Kaiser study released this week. In some clusters, up to 23 percent of children are not fully vaccinated, according to the study.

Majority of cases

In Southern California, where the majority of cases in the current outbreak have been reported, several schools have had to tell unvaccinated children to remain home when a case was found in a student. The incubation period for measles is as long as three weeks.

Forty-two of the cases have been directly linked to the Disney outbreak, meaning the infected person had either been to Disneyland or California Adventure Park or had direct contact with someone who had been to the parks. Several of those infected are Disney employees.

The source of the remaining cases isn’t clear, but they may be indirectly tied to the Disney outbreak, public health officials said. For example, someone could have gotten sick at Disneyland in December but never been diagnosed, then sickened others in a different public place such as a school or shopping area.

“It’s pretty clear we’ve seen some cases that go beyond the initial outbreak of Disneyland. That tells me you’re having transmission that’s occurring in our communities now,” said Dr. Stephen Parodi, director of hospital operations for Kaiser Northern California. Kaiser doctors have treated several patients since the outbreak began, he said.

“California had a large outbreak of measles back in the early 1990s that was related to under-vaccination of people. That turned into a 6,000- to 8,000-person outbreak,” Parodi said. “We have the opportunity now to avoid that. If we bring people in and get the measles vaccine we can prevent it.”

Erin Allday is a San Francisco Chronicle staff writer. E-mail: eallday@sfchronicle.com