California public health authorities have conducted genetic tests on the virus that caused the measles outbreak sweeping the country, but that has not led them to the source of the outbreak so far.
Writing in the Morbidity and Mortality Weekly Report produced by the Centers for Disease Control and Prevention, state public health officials said they had genotyped the virus from 30 of 110 California residents who contracted the disease but still cannot determine the source of the outbreak, which began in late December in two adjacent Disney theme parks in Southern California.
All the specimens "were measles genotype B3, which has caused a large outbreak recently in the Philippines, but has also been detected in at least 14 countries and at least six U.S. states in the last 6 months," they wrote. The Philippines had more than 53,000 confirmed cases of the measles last year.
"International travel to countries where measles is endemic is a well-known risk factor for measles, and measles importations continue to occur in the United States," they wrote in the report, which was released late Friday. "However, U.S. residents also can be exposed to measles in the United States at venues with large numbers of international visitors, such as other tourist attractions and airports. This outbreak illustrates the continued importance of ensuring high measles vaccination coverage in the United States."
The CDC said last week that 121 people in 17 states and the District of Columbia had come down with the measles. Authorities have blamed the spread of a disease that was eliminated in 2000 largely on people who, for personal or religious reasons, are choosing not to have their children vaccinated or are delaying their immunizations.
Update: On Tuesday afternoon, the CDC said the number of cases had grown to 141 in 17 states and Washington, D.C. an increase of 20 cases over the past week.
Among the 110 California patients, "49 (45%) were unvaccinated; five (5%) had 1 dose of measles-containing vaccine, seven (6%) had 2 doses, one (1%) had 3 doses, 47 (43%) had unknown or undocumented vaccination status, and one (1%)" appeared to have been vaccinated or was previously infected by measles, the officials wrote. Twelve of the unvaccinated patients were infants who could not be vaccinated because they were too young; the measles vaccine is not recommended for children under a year of age. Among the other 37, "28 (76%) were intentionally unvaccinated because of personal beliefs, and one was on an alternative plan for vaccination," they wrote.
Fifteen cases have been linked to the theme park exposure in six other states -- Arizona (seven), Colorado (one), Nebraska (one), Oregon (one), Utah (three) and Washington (two). There also have been 10 cases in Canada and one in Mexico, they wrote.