At least 1,500 people in New York, most of them Orthodox Jews, have contracted mumps during a seven-month outbreak that began last summer in a boys camp in the Catskill Mountains, the Centers for Disease Control and Prevention reported Thursday in its Morbidity and Mortality Weekly Report. Almost all of those infected had received the mumps vaccine, which suggests that crowded households and close contact in schools can sometimes overwhelm the protective effects of immunization. A few cases were reported outside the religious community, but none of those led to sustained transmission.
The outbreak is the largest in the United States since 2006, when almost 6,600 cases were reported in six Midwestern states. In a normal year, about 300 cases are reported nationwide.
Mumps is marked by a swelling of the salivary glands, giving the victim a characteristic chipmunk-like appearance. Most victims have fever and headache, and a few suffer from hearing loss, meningitis and swollen testicles that can lead to infertility. It was once a common disease in the U.S., with an average of 186,000 cases per year before the mumps vaccine, now included in the mumps-measles-rubella, or MMR, vaccine was introduced in 1967. The mumps part of MMR is thought to be the least effective of the three vaccines, with 73% to 91% of those vaccinated obtaining proteciton after one dose and 79% to 95% after two doses.
Patient zero in the current outbreak was an 11-year-old boy who returned from England on June 17. Mumps has become more common in that country recently because of the substantial number of parents who refuse to let their children receive the MMR under the misguided belief that the vaccine can cause autism. About 7,400 cases of mumps were reported in Britain last year.
Right after his return, the boy attended a summer camp for tradition-observant Jewish boys, where symptoms of the disease became apparent. Shortly thereafter, other boys at the camp and one staff member developed symptoms. After the campers returned home, transmission continued in the community. As of Jan. 29, 1,521 cases had been reported, a sharp increase from the 179 cases reported through the end of last October.
Orthodox Jews have accounted for more than 97% of cases, and the majority -- 61% - -are among 7- to 18-years-old. More than three-quarters of the patients are male. Among those for whom vaccination status is known, 88% had received one dose of MMR and 75% had received two doses.
Epidemiologist Kathleen Gallagher of CDC, the lead author of the study, attributes the infections to unique characteristics of the religious communities. The mean household size of the affected communities is 5.7 people, compared with the U.S. average of 2.6. That means family members spend much more time in close contact, which can enhance transmission. Moreover, the boys mostly attended Hebrew school, where they have a longer day than public school students and sit facing each other at study tables, rather than all facing the front of the room. The face-to-face position encourages the spread of germs, Gallagher said.
Despite the relatively high number of cases, the fact that even more have not been infected and that the outbreak has not spread through the community at large shows that vaccination is still effective in preventing spread of the disease, she said.
-- Thomas H. Maugh II
Adriana Colin holds her son Andrew as he receives the MMR vaccine. Credit: Los Angeles Times / Anacleto Rapping