Mumps Outbreak In United States Orthodox Jewish Communities, 2009-10

Background: Mumps is an acute, viral illness that commonly presents with parotitis or other salivary gland swelling, fever, and malaise. Complications include meningitis, pancreatitis, and orchitis in post-pubertal males. One dose of vaccine is ~80% effective at preventing disease (range 73-91%), and 2 doses are ~90% (range 79-95%). Despite high two-dose vaccine coverage, several Orthodox Jewish communities in the Northeastern United States (US) experienced a large mumps outbreak in 2009-10.

Objectives: We describe the epidemiologic characteristics of this outbreak.

Methods: Local and state health departments collected case-specific data, including demographics, clinical symptoms, and vaccination history. Criteria for laboratory confirmation included the presence of either mumps-specific IgM in serum samples or mumps virus or mumps RNA in buccal swabs.

Results: From June 28, 2009 to June 27, 2010, 3502 outbreak-associated cases of mumps were reported in the Northeastern US.  The outbreak was largely confined to Orthodox Jewish communities. Transmission was focused in yeshivas (religious Jewish schools). Most case-patients were school-aged boys (53.3% were 5-17 years-old, and 70.8% were male). Vaccination status was reported for 71.9% of case-patients, and of these, 75.5% had received 2 MMR doses, 14.1% 1 dose, and 10.4% 0 doses. There were 41 hospitalizations and 145 complications including Bell’s palsy (1), deafness (3), encephalitis (3), mastitis (1), meningitis (8), oophoritis (5), orchitis (120), and pancreatitis (4). Forty-seven percent of cases had laboratory testing, and of these, 50.4% were confirmed by serology or virus detection.

Conclusions: Although most disease occurred in fully vaccinated individuals, high two-dose coverage likely limited the scope of this outbreak and prevented spread to other communities. Limited vaccine effectiveness, waning immunity, and intense exposures likely contributed to this outbreak. Given the constant threat of imported disease and ongoing endemic transmission, efforts should be made to maintain high vaccination coverage.