State and local health departments in New York and New Jersey, in collaboration with the Centers for Disease Prevention and Control (CDC), continue to investigate a mumps outbreak that began in New York in June 2009.
The index case occurred in a boy aged 11 years who had returned on June 17 from a trip to the United Kingdom, where approximately 7,400 reports of laboratory-confirmed mumps were received by the Health Protection Agency in 2009. He then attended a New York summer camp for tradition-observant Jewish boys, where he became symptomatic on June 28. Subsequently, other camp attendees and a staff member were reported to have mumps, and transmission continued in multiple locations when the camp attendees returned home. As of Jan. 29, 2010, a total of 1,521 cases had been reported, with onset dates from June 28, 2009, through Jan. 29, 2010, a substantial increase from the 179 cases reported as of October 30, 2009.
The outbreak has remained confined primarily to the tradition-observant Jewish community, with <3 percent of cases occurring among persons outside the community. The largest percentage of cases (61 percent) has occurred among persons aged 7 to 18 years, and 76 percent of the patients are male. Among the patients for whom vaccination status was reported, 88 percent had received at least 1 dose of mumps-containing vaccine, and 75 percent had received 2 doses. This is the largest mumps outbreak that has occurred in the United States since 2006. Although mumps vaccination alone was not sufficient to prevent this outbreak, maintaining high measles, mumps, and rubella (MMR) vaccination coverage remains the most effective way to prevent outbreaks and limit their size when they occur.
Mumps cases included in this report were reported by Jan. 29, 2010. Cases were classified according to the 2008 case definition of the Council of State and Territorial Epidemiologists; only cases of probable and confirmed mumps are included in this report. In the United States, the Advisory Committee on Immunization Practices (ACIP) recommends that children receive 2 doses of measles, mumps, and rubella (MMR) vaccine, with the first dose administered at 12-15 months and the second dose near the time of school entry (at 4-6 years). Methods used to obtain the vaccination status of patients have included parental report, review of vaccination cards, and verification from healthcare providers.
The 1,521 outbreak-related mumps cases have been reported from several counties in New York and New Jersey; local transmission is continuing (Figure). The majority (675 [44 percent]) of cases have been reported from New York City (primarily Brooklyn), followed by Orange County, New York (364 [24 percent]); Rockland County, New York (298 [20 percent]); and four counties in New Jersey (159 [10 percent]). Twenty-five (2 percent) cases (reported during June 28--September 8) were associated with the summer camp in Sullivan County, New York; however, no additional cases occurred in the county after the camp ended in late August. Of the 1,521 patients, 1,477 (97 percent) are members of the tradition-observant Jewish community. Of the 44 cases not associated with this religious community, 33 have been reported from New York City; seven from New Jersey; two from Orange County, New York; and two from Rockland County, New York. Many of these outside cases have occurred among persons who have reported regular contact with members of the affected community.
Diagnostic laboratory testing for mumps (i.e., detection of mumps immunoglobulin M antibodies by various methods, detection of mumps RNA by real-time reverse transcription--polymerase chain reaction, or isolation of mumps virus in cell culture) has been performed for 761 (50 percent) cases. Of these, 385 (51 percent) cases are laboratory confirmed.
Of the 1,518 patients whose age is known, 1,385 (91 percent) are aged >6 years (Figure). The median age of patients is 15 years (range 3 months--90 years) and is similar in all areas with ongoing transmission except New Jersey, where the median age is 17 years. Of the 1,489 patients whose sex is known, 1,136 (76 percent) are male. Sixty-five reports of complications from mumps have been received: orchitis (55 cases), pancreatitis (five cases), aseptic meningitis (two cases), transient deafness (one case), Bell's palsy (one case), and oophoritis (one case). Nineteen hospitalizations from mumps have been reported; no deaths have occurred.
Vaccination status is known for 1,115 patients: 966 (91 percent) of 1,062 patients aged ≤18 years and 149 (33 percent) of 456 patients aged ≥19 years (Table). Of these patients, 976 (88 percent) had received at least 1 dose of mumps-containing vaccine before the outbreak, and 839 (75 percent) had received 2 doses. Among patients aged 7--18 years, the age group with the majority of cases and for whom 2 doses of MMR vaccine is recommended, 93 percent had received at least 1 dose, and 85 percent had received 2 doses. The vaccination status of the patients varies by location. The percentage of patients aged >6 years (for whom vaccination status is known) who had received 2 doses of mumps vaccine is highest in Orange County, New York (86 percent), followed by New York City (83 percent), New Jersey (76 percent), and Rockland County, New York (73 percent).
Public health response measures in all affected areas have continued throughout the outbreak. Health-care providers have been notified about the ongoing outbreak, the importance of verifying that children have received all recommended vaccinations, and the need to offer vaccinations to adults with unknown vaccination status who do not have a history of mumps. State and local health departments also have worked with affected schools to enhance vaccination policies, including policies to exclude unvaccinated children from school during outbreaks and to isolate children at home for 5 days after onset of parotitis. Certain jurisdictions have encouraged providers to offer a second dose of MMR vaccine to children aged 1--4 years; however, this strategy has not been a focus of the public health response because of the small proportion (4.9 percent) of cases reported in this age group.
Beginning on Jan. 19, 2010, in Orange County, New York, public health officials began offering a third dose of MMR vaccine in three schools where, despite documentation of a high level of 2-dose coverage among students, transmission had continued for >2 months. This intervention is being carried out under an Institutional Review Board--approved protocol that provides for an evaluation of the impact of the intervention.
Reference: CDC. Mumps outbreak -- New York, New Jersey, Quebec, 2009. MMWR 2009;58:1270--4.