Mumps, 2017

In 2017, 72 mumps cases were reported. Sixty-one (85%) were classified as confirmed (tested positive by PCR), and 11 (15%) as probable (tested positive by IgM serology, or were epidemiologically-linked to another case or outbreak). Of the confirmed cases, 53 (87%) were genotyped as G which is the dominant genotype circulating in the United States since 2006, and 1 (2%) was genotyped as J and was related to international travel to Indonesia.

Sixty-two (86%) cases were related to three distinct outbreaks that occurred in Minnesota. The largest outbreak (45 cases, 63%) at the University of Minnesota Twin Cities campus began after multiple students came back from spring break in Texas with mumps. Five cases (7%) were related to an isolated outbreak occurring among Minnesota Wild National Hockey League players and staff, and 12 cases (16%) were related to an outbreak in an under- vaccinated community in Polk County. Ten additional cases (14%) were not outbreak-related; 2 cases acquired mumps from recent international or domestic travel, and 8 sporadic cases were not linked to outbreaks occurring within Minnesota or elsewhere.

The median age of cases was 22 years (range 1 to 57). Ten cases (14%) occurred in persons <18 years of age, 56 cases (78%) occurred in persons 18-49 years, and 6 cases (8%) occurred in persons ≥50 years of age. Seventy cases (97%) experienced parotitis, and 3 (4%) reported orchitis. One adult was hospitalized for 2 days with fever and myalgia and recovered without complications.

Nineteen (26%) cases reported a history of receiving at least 1 dose of mumps-containing vaccine but had no documentation of those doses. Thirty- eight cases (53%) had a documented history of receiving 1 or 2 doses of mumps-containing vaccine. Eleven (15%) cases were unvaccinated, and 4 (6%) reported unknown vaccination status. No case reported a previous history of mumps disease.

Mumps surveillance is complicated by nonspecific clinical presentation in nearly half of cases, asymptomatic infections in an estimated 30% of cases, and suboptimal sensitivity and specificity of serologic testing.

A number of viruses can cause sporadic parotitis including human herpes virus 6, enterovirus, Epstein- Barr, lymphocytic choriomeningitis virus, bocavirus, and human immunodeficiency virus. Acute bacterial parotitis may present with unilateral swelling. Noninfectious causes include drugs, tumors, and immunologic diseases.

• For up to date information see>> Mumps
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2017