RENEE MONTAGNE, HOST:
California officials say a measles outbreak that started in Disneyland has sickened 59 people in California and eight more across Oregon, Washington, Utah, Colorado and Mexico. As NPR's Patti Neighmond reports, the outbreak is large compared to other years, and most of those who got sick were not vaccinated.
PATTI NEIGHMOND, BYLINE: In the year 2000, the U.S. was declared measles-free. That's because vaccine rates are so high that everyone, even those who don't vaccinate their children, generally benefit from mass immunity. But those unvaccinated children are still vulnerable. State health officials have not identified the individual who brought the virus to Disneyland, but Dr. William Schaffner, infectious disease specialist at Vanderbilt Medical Center, says it was likely someone who lives outside the Western Hemisphere where the virus can be epidemic.
WILLIAM SCHAFFNER: This is the most communicable virus we know.
NEIGHMOND: It spreads easily through the air even before infected individuals get sick.
SCHAFFNER: It can float in the air in an enclosed space. And you leave - you're the spreader - and then a susceptible person can come in a half hour later, breathe the air that contains the virus and they can get sick. No other virus that we know spreads that readily.
NEIGHMOND: So places where crowds gather, like theme parks with long lines and closed rides and lots of hotels and restaurants, are ideal environments for the virus which causes fever, cough and a spotted body rash to spread. People who have gotten the two-dose vaccine are 99 percent protected, but others are susceptible - those with weakened immune systems and infants under the age of 1 before the first vaccine dose is given.
SCHAFFNER: And if infants acquire measles, then they are at high risk of developing the complications of middle ear infection and pneumonia and requiring hospitalization.
NEIGHMOND: Children whose parents are concerned about vaccine safety and don't immunize them are also at risk. There are no problematic side effects of the measles vaccine, and theories about links to autism have been thoroughly debunked.
At UCLA, Dr. Nina Shapiro, a pediatric ear, nose and throat surgeon, says parents can be vague about whether their child is fully vaccinated or not. Take this recent visit with a parent of a 9-week-old baby who had a severe cough.
NINA SHAPIRO: She has five older children at home, and I asked a very simple question which was, are the other children at home immunized? And she said, yes, yes, they're all fully up-to-date with their immunizations.
NEIGHMOND: When Shapiro called the pediatrician to follow up on the patient...
SHAPIRO: The pediatrician said that nobody in that house has had one immunization.
NEIGHMOND: Shapiro speculates parents who don't vaccinate their children may feel marginalized or embarrassed.
SHAPIRO: If a physician says, well, I assume your children are immunized, it's hard to say no.
NEIGHMOND: Shapiro suggests doctors approach the issue more tactfully by discussing risks of diseases that can be prevented with vaccines. State health officials say the number of people getting sick with measles as a result of the initial Disneyland exposure can be expected to rise. Patti Neighmond, NPR News. [POST-BROADCAST CORRECTION: We say the measles vaccine causes no problematic side effects. According to the Centers for Disease Control and Prevention, most children do not have any side effects from the shot. The side effects that do occur are usually very mild, such as a fever or rash. More serious side effects are rare. These may include high fever that could cause a seizure.] Transcript provided by NPR, Copyright NPR.