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Mumps is an acute, self-limited, systemic viral illness typically characterized by parotitis or other salivary gland swelling. Although mumps was once considered a universal childhood disease in the United States, routine mumps vaccination had led to a >99% reduction in cases by the early 2000s. However, since 2006, there has been an increase in mumps cases in this country, the majority among fully vaccinated persons. Mumps should be suspected in all patients with parotitis or mumps complications (see “Clinical Manifestations”), regardless of age, vaccination status, or travel history.
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Mumps is an acute viral illness caused by a paramyxovirus from the Rubulavirus genus in the Paramyxoviridae family. This single-stranded, negative-sense, enveloped RNA virus is ~15.3 kb in size and encodes several minor proteins and seven major proteins. Mumps virus is rapidly inactivated by formalin, ether, chloroform, heat, and ultraviolet light. There is only one mumps virus serotype. One of the seven major encoded proteins, the small hydrophobic (SH) protein, exhibits hypervariability among strains; thus, the SH gene nucleotide sequence is used to genotype the virus for molecular epidemiologic purposes.
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The 12 known genotypes of mumps virus are designated by the letters A to N (except E and M). In the United States, >98% of mumps virus specimens genotyped from 2015 through 2017 were genotype G. Most mumps vaccines licensed globally are composed of virus strains from genotype A, B, or N. The mumps virus strain (Jeryl Lynn) used in vaccines in the United States is genotype A.
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Mumps occurs worldwide and is endemic in many countries. In the absence of routine vaccination, the incidence of mumps is 100–1000 cases per 100,000 population, with epidemic peaks every 2–5 years. From 1999 through 2019, on average, >500,000 mumps cases were reported to the World Health Organization annually; however, global mumps incidence is challenging to estimate, as few countries routinely collect data on mumps incidence. Since 2018, mumps vaccine is routinely used in 122 countries. Mumps incidence has been reduced by 97–99% in countries with a routine two-dose measles, mumps, and rubella (MMR) vaccination schedule and by 87–88% in those with a one-dose vaccination program. However, since the mid-2000s, large mumps outbreaks have been reported among populations with high two-dose MMR coverage in countries with routine mumps immunization programs. Most outbreaks have occurred in settings with intense or frequent close contact, such as universities, close-knit communities, and correctional facilities, and most cases have occurred in fully vaccinated persons. Despite these outbreaks, mumps incidence is still much higher in countries that do not have routine mumps vaccination.
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In the United States, prior to licensure of a vaccine for mumps in 1967, >100,000 mumps cases occurred annually. After the implementation of a one-dose mumps vaccination policy in 1977 and a subsequent two-dose policy in 1989, reported mumps cases declined to ...