Mumps virus nomenclature update: 2012.

A report based on the WHO Mumps Nomenclature Update Meeting, Geneva, 22 September 2011
Mumps is a highly contagious vaccine preventable disease caused by mumps virus (MuV). The infection is sub-clinical in up to 30% of cases and asymptomatic infection is more common in adults than in children. Reinfection may occur after either natural infection or vaccination. The main clinical manifestations of mumps are parotitis (90% of cases), aseptic meningitis (~15% of cases), transient deafness (~4%) and encephalitis (~0.1%). Other clinical features include orchitis (20–38% of postpubertal male cases), oophoritis (0.5–7% of female cases) and up to 40–50% of mumps infections result in respiratory symptoms. In the absence of vaccination, mumps annual incidences range from between 100 to1000 cases per 100 000 population with epidemic peaks occurring every 2 to 5 years, usually in winter and spring. In countries with high vaccination coverage, the percentage of cases with encephalitis and the other severe reactions described above is greatly reduced.1 During a mumps outbreak, the clinical diagnosis is not difficult in patients with parotitis and a history of recent exposure; however, when disease incidence is low, other causes of parotitis should be considered and laboratory testing for mumps is required for case confirmation.