During 2012, no cases of confirmed mumps were reported but there were 7 cases of probable mumps. Beginning in 2012, national case reporting criteria for mumps were revised. Confirmed cases must now be laboratory-confirmed by PCR and present with clinically compatible illness defined as acute parotitis or other salivary gland swelling lasting at least 2 days, aseptic meningitis, encephalitis, hearing loss, orchitis, oophoritis, mastitis or pancreatitis. Probable cases are now reportable and require a positive mumps IgM antibody test result and/or epidemiologic linkage to another probable or confirmed case. Additionally, probable cases must present with clinically compatible illness defined as acute parotitis or other salivary gland swelling lasting at least 2 days, orchitis or oophoritis.
Six of the 7 probable cases of mumps were confirmed by IgM serology, and 1 was epidemiologically linked to an IgM-positive household contact. The 6 IgM-positive probable cases were not epidemiologically linked, demonstrating that asymptomatic infections are occurring, and suggesting that mumps is underdiagnosed. Cases ranged from 10 to 70 years of age. Two cases were born before 1957 and had unknown vaccination and disease history, 4 were fully vaccinated (2 self-reported, 2 had documentation of vaccination), and 1 had an unknown vaccination history.
Mumps surveillance is complicated by nonspecific clinical presentation in nearly half of cases, asymptomatic infections in an estimated 20% of cases, and suboptimal sensitivity and specificity of serologic testing. Mumps should not be ruled out solely on the basis of negative laboratory results. Providers are advised to test for other causes of sporadic parotitis including parainfluenza virus types 1 and 3, Epstein-Barr virus, influenza A virus, group A coxsackievirus, echovirus, lymphocytic choriomeningitis virus, human immunodeficiency virus, and other noninfectious causes such as drugs, tumors, and immunologic diseases.
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