Mumps virus causes a childhood disease that is characterised by swelling of the salivary glands (parotitis) and the testes (orchitis). Though it causes what is usually a mild disease infection, in adolescents and adults, it can be seriously discomforting and lead to meningitis and other sequelae. It was the main cause of viral meningitis before vaccines controlled the numbers of cases. Some of the clinical signs develop only after the onset of immune responses and may result from immunopathological reactions. Its pathogenesis is not well understood and relatively under researched for a human pathogen. Mumps virus is a nonsegmented negative-stranded ribonucleic acid virus belonging to the family Paramyxoviridae. The molecular description of the virus, the understanding of the genome expression and the role of most viral proteins, though far from completely understood, has advanced in recent years and we are now able to introduce mutations into the virus at will and make recombinant viruses that express autofluorescent proteins or other foreign proteins from additional transcription units within the genome and hence the opportunity exists now to study pathogenesis in a number of animal and human tissue models using novel bioimaging modalities.

Key Concepts:

• Mumps virus is a relatively simple enveloped, negative-sensed RNA virus which contains only seven genes.
  
• Mumps virus is a highly infectious agent which causes a relatively mild systemic disease in susceptible individuals.
  
• A highly efficacious vaccine has been developed, although the molecular basis of the attenuation remains an enigma.
  
• Inadequate virus attenuation caused aseptic meningitis in vaccinees and resulted in the withdrawal of mumps vaccines, public resistance to vaccination in the 1990s. In some countries, such as Japan this led to the complete cessation of national vaccination programmes.
  
• Recombinant mumps viruses have helped to define the molecular determinants of neurotropism.