Multicounty Community Mumps Outbreak — Ohio, January–September 2014

BACKGROUND:   On March 6, 2014, the Ohio Department of Health (ODH) received a report of a mumps outbreak involving 9 university students. During the following weeks, ODH detected increased mumps incidence in three counties surrounding the university. Widespread community mumps transmission is rare in the postvaccine era. We investigated to identify and prevent additional cases.

METHODS:   A probable case was defined as parotitis lasting ≥2 days or unexplained orchitis or oophoritis, with onset on or after January 1, 2014, and an epidemiologic link (e.g., residence or employment) with one of three affected counties. Case confirmation required positive reverse transcription-polymerase chain reaction or culture for mumps. Mumps is a reportable condition in Ohio. For each reported case, local health officials conducted patient interviews and reviewed medical charts, laboratory findings, and vaccination records.

RESULTS:   We identified 484 cases, 34 (7%) laboratory-confirmed, from January 1–September 20. Illness onset primarily occurred during March–May. Median patient age was 23 (range: 0.3–80) years. Thirty-three patients (6.8%) experienced complications; 14 were hospitalized. Overall, 195 patients (40.3%) reported they were students or employees at the university, 59 more had an epidemiologic link to the university, and 20 additional patients shared an employer or school with a university-linked patient. Of 243 patients with known vaccination status, 200 (82.3%) had received ≥1 and 149 (61.3%) had received ≥2 mumps vaccinations; 43 (17.7%) were unvaccinated. To prevent further transmission, 1,346 mumps-containing vaccine doses were given throughout the affected counties.

CONCLUSIONS:   This was the largest U.S. mumps outbreak since 2010 and was unique because of widespread community transmission. Integration between the university and surrounding community likely contributed to the substantial number of community cases.