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Mumps is a communicable, systemic viral illness most often characterized by parotitis. With widespread use of mumps vaccine in over 114 countries worldwide currently, the disease has become less common. However, due to waning vaccine immunity over time, some disease continues to occur in sporadic outbreaks. A significant number of mumps infections are asymptomatic.
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EPIDEMIOLOGY AND PATHOGENESIS
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Humans are the only known natural host of mumps virus, a paramyxovirus closely related to parainfluenza viruses. Mumps is spread by respiratory droplet or through direct contact with saliva. The virus can be isolated from saliva up to 7 days before and through 8 days after parotid swelling. Mumps virus is less contagious than either measles or varicella virus; typically, the incubation period is 16 to 18 days (range, 12–25 days).
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A live attenuated mumps virus vaccine was first licensed in the United States in 1967. In the prevaccine era, the incidence of mumps was 50 to 251 cases per 100,000. Following implementation of a single-dose vaccine recommendation, the incidence markedly declined to 2 per 100,000 by 1988. After implementation of a 2-dose recommendation for measles-mumps-rubella vaccine in 1989, mumps incidence declined further to 0.1 case per 100,000 by 1999. By 2005, mumps disease rates had declined 99% compared to the prevaccine era. However, over the past decade, periodic outbreaks of mumps disease have continued to occur, especially in adolescents and young adults, many of whom have received either 1 or 2 doses of vaccine as young children. It is estimated that 1 dose of mumps vaccine is 78% (range, 49–92%) effective and 2 doses of vaccine are 88% (range, 66–95%) effective in preventing mumps disease.
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In susceptible, unimmunized populations, 60% to 70% of cases of mumps are associated with parotitis. However, up to 33% of mumps infections may go unrecognized, especially in adults, because the cases do not have parotitis. Given the number of subclinical cases, information regarding a patient’s history of mumps infection is notoriously inaccurate.
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Following transmission of mumps virus to a susceptible host, the primary site of viral replication is the epithelium of the upper respiratory or gastrointestinal tract or the eye. The virus then quickly spreads to the local lymphoid tissue, and a primary viremia ensues. The parotid gland, central nervous system (CNS), testis or epididymis, pancreas, and/or ovary may be involved. Inflammation in these infected tissues then leads to characteristic symptoms such parotitis, aseptic meningitis, and/or abdominal pain. A secondary viremia occurs a few days after symptoms of illness begin, indicating viral replication within target organs. Virus can be identified in urine for up to 2 weeks following onset of clinical illness.
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Lifelong immunity develops in virtually all patients after natural infection, although a second infection has been reported to occur very rarely.
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CLINICAL MANIFESTATIONS
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A patient with mumps rarely ...