BACKGROUND: Since 2006, mumps outbreaks on college campuses have occurred frequently. In 2016, the Indiana State Department of Health and local health departments investigated outbreaks of mumps at four universities in Indiana. Our study aims to characterize the outbreaks, community spillover, and control measures utilized by public health departments to mitigate spread.
METHODS: Reported mumps infections with onset between January 1 and September 10, 2016 were classified as probable or confirmed using the 2012 Council of State and Territorial Epidemiologists case definition. Case investigations were conducted to collect information about clinical presentation, vaccination status, and laboratory testing, and initiate control measures. To mitigate the impact of each outbreak, vaccination clinics were held and case detection activities were initiated, including increased testing at the state public health laboratory and public health messaging of testing recommendations, disease information, and outbreak updates.
RESULTS: A total of 281 confirmed and probable mumps cases were identified between January 1, 2016 and September 10, 2016. Of these, 179 cases (63.7%) occurred in students or staff affiliated with the four outbreak universities and 102 (36.3%) occurred in community members, of whom 26 (25.5%) had known epidemiological links to other cases. One case was hospitalized and 74 (26.3%) cases visited an emergency room. Complications, including orchitis and meningitis, were reported among 2.1% of cases. The state and local health departments disseminated 46 public health messaging documents to providers, partners, and the public. The ISDH Laboratory tested 504 specimens from 488 unique patients for confirmation by polymerase chain reaction (PCR) and 42.7% were positive. Among 19 cases who had PCR or culture positive tests and also had a serum immunoglobulin M (IgM) test, 11 cases were IgM negative and 8 cases were IgM positive. Documentation of two or more doses of mumps-containing vaccine was available for 84.9% of university cases and 52.0% of community cases. Seven vaccination clinics were held across three of the four universities, during which a total of 5,273 doses of measles-mumps-rubella (MMR) vaccine were administered.
CONCLUSIONS: These outbreaks occurred in highly vaccinated populations and resulted in community spillover of cases. Laboratory testing during this outbreak supports concerns around routine use of IgM testing in vaccinated persons previously described in the literature. Improved baseline mumps surveillance and interstate collaboration are needed to better understand mumps resurgence on college campuses and to share best practices for outbreak testing, communications, and management.