The current outbreak of measles that began at the Disneyland park in Anaheim, Calif., is unusual in several ways, a top CDC official said Thursday, but one aspect is disturbingly familiar: most of those contracting the disease apparently were not vaccinated.
Anne Schuchat, MD, director of the CDC's National Center for Immunization and Respiratory Diseases, told reporters on a conference call that 84 people in 14 states have been diagnosed with measles so far in 2015 and, of them, 67 are linked to the Disneyland outbreak.
There have already been more cases in January than the median full-year count over the past decade, she said.
The Disneyland outbreak's source has not been identified, Schuchat said, but she called it "likely" that it started with a traveler who contracted the infection overseas. She said measles is still not indigenous in the U.S., having been nearly eradicated by vaccination; index cases in recent outbreaks have all been people who brought the virus from other countries where measles is still endemic.
Those individuals whom officials believe contracted the infection at Disneyland did so from Dec. 17-20, Schuchat said. The continuing outbreak is now the result of those individuals spreading the virus into their own communities. Measles is highly contagious, she noted, with 90% of people in the same room with an infected person likely to become infected themselves if they are not already immune. Measles is communicable before symptoms appear, she said.
Among the settings where public health officials believe transmission has occurred are outpatient clinics and emergency departments, Schuchat noted.
She reminded reporters that measles is still a major problem elsewhere in the world, with nearly 150,000 deaths occurring globally in 2013.
The Disneyland-centered outbreak is "a wake-up call" for Americans to be vaccinated so that future imported cases don't spread.
"The majority of adults and children reported to us [in the current outbreak], for whom we have information, had not been vaccinated, or did not know whether they had been vaccinated," she said.
Last year had the largest number of measles cases seen in 20 years, a total of 644. Most of these were linked in some way to a large outbreak in the Philippines, where some 50,000 cases were diagnosed, Schuchat said.
She pointed to incomplete vaccination in many areas as a contributor to the recent U.S. outbreaks, noting that 19 states had less than 90% vaccination coverage for school-age children in the most recent tally.
She called on physicians and other providers to "think measles" when they encounter patients with fever and rash, the hallmark symptoms.
Current vaccination recommendations are for the first dose in children to be administered at 12 months of age with a booster at 4-6 years of age, although it can be given sooner. Adults should receive two doses.
Schuchat said adults who are unsure if they were previously vaccinated should have it now. "There's no harm in getting another MMR vaccine," she said.