Mumps outbreaks at four universities--Indiana, 2016

The United States experienced its biggest outbreak of mumps in a decade during 2016, largely due to a cluster of infections at four universities between February and April of that year.

The United States experienced its biggest outbreak of mumps in a decade during 2016, largely due to a cluster of infections at four universities between February and April of that year. In all, there were 237 confirmed infections and another 44 labeled as probable in the Indiana outbreaks—including more than 100 community cases that occurred among patients with no connection to any of the campuses. State health officials were able to epidemiologically link only about 25% of those community cases to the university outbreaks, however. This shortcoming could signal gaps in current finding and linkage methods, unwitting transmission due to an absence of symptoms, or underreporting during nonoutbreak periods. In fact, nearly a quarter of those affected by the Indiana university events lacked documentation of immunity—such as proof of vaccination with two doses of measles, mumps, and rubella vaccine. The finding speaks to the importance of standardizing immunization documentation requirements at universities to dovetail with CDC and state recommendations for proof of immunity. The Indiana experience also underscores the role of lab testing. During the outbreaks, a protocol describing recommended testing, testing priorities during the outbreak, and a preauthorization process for submitting specimens to the state lab was drawn up and distributed. The plan increased the share of specimens testing positive, from 25.8% in the weeks before the protocol was implemented to nearly 38% in the weeks after adoption. Outbreak-specific lab test guidance on specimen collection for mumps verification also could improve case detection and facilitate outbreak management, according to CDC researchers.