Multi-State Mumps Outbreak in 2009 — New York City (NYC) Experience

Background: Mumps is an acute viral infection characterized by parotitis and orchitis and was a leading cause of aseptic meningitis and deafness before vaccine introduction.  Reported incidence of mumps was 50-241/100,000 before vaccine licensure. By 2005, there was a 99% reduction in mumps incidence. In 2006, a major resurgence occurred in the Midwest predominantly among vaccinated college students. On August 18, 2009, an outbreak of mumps was reported among boys, many from NYC, attending a camp in Sullivan County, NY. 

Objectives: To describe the current status of the resulting mumps outbreak in NYC.

Methods: Surveillance and investigation of mumps cases in NYC was conducted in accordance with CDC surveillance manual protocols including laboratory testing for mumps IgM  and IgG serology, PCR and culture. 

Results: The index camp case had onset of disease on June 28, 2009 after returning from England. The majority (20/25, 80%) of cases at the camp were NYC residents who were all members of an observant religious community.  As of November 25, 247 cases were confirmed among NYC residents; 84% were in this same religious community. Overall, 66% of cases have been of school age (6-20years); 81% are male; 55% of all cases and 76% of school age children have documentation of two doses of mumps-containing vaccine; 20% have unknown vaccination status, predominantly among older cases. Most (82%) cases had laboratory testing: among lab confirmed cases, 48% were positive by PCR and 62% by serology. Complications have included: orchitis (6%), pancreatitis (<1%) and meningitis (<1%); 2% of cases were hospitalized. 

Conclusions:Mumps transmission has been sustained despite high levels of vaccination among cases. Factors contributing to ongoing transmission, such as population density and behavioral factors, are being investigated. Addressing the limits of mumps vaccine efficacy may be needed to achieve mumps elimination.