Mumps viruses are RNA viruses of the family Paramyxoviridae. The virions are spherical particles of 150-250 nm in diameter consisting of a ribonucleoprotein with helical symmetry and enveloped by matrix protein and a lipid bilayer that contains two spike line structures: viral hemagglutinin (H) and viral neuraminidase (N).

Mumps virus involves primarily the parotid and related salivary glands; however, the infection can lead to CNS disease and accumulation of the virus in CSF. Mumps (Epidemic Parotitis) is an acute contagious viral disease mostly occurring in children.

 Nearly 50% of all infections are subclinical. The highest incidence of clinical manifestations is found in the age group of 4 to 15 years. Secondary infections are rare because of long-lasting immunity. 10 to 35 % of mumps cases develop orchitis which occurs nearly always after puberty.

The process is mostly unilateral and the prognosis is usually good. Mumps virus has been one of the most important causes of viral CNS disease (meningitis and encephalitis) in the USA; vaccine administration has greatly reduced its incidence.