Acute Mumps

Updated: Nov 06, 2015
  • Author: Yonatan Yohannes, MD; Chief Editor: Jeter (Jay) Pritchard Taylor, III, MD  more...
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Overview

Background

Mumps is a systemic illness caused by the paramyxovirus. It is a human disease that occurs worldwide. The mumps vaccine was introduced in 1967, and the disease became nationally reportable in 1968. The incidence has decreased substantially with vaccination, but periods of resurgence have occurred in recent years. [1]

See the Centers for Disease Control and Prevention (CDC) recommended immunization schedule for persons aged 0 through 18 years, [2] the catch-up schedule for persons aged 4 months through 18 years, [3] and the adult immunization schedule for persons older than 18 years. [4] See the full recommendations for the measles, mumps, rubella (MMR) and measles, mumps, rubella, varicella (MMRV) vaccines from the Advisory Committee on Immunization Practices, [5] including benefit versus risk profile and contraindications.

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Pathophysiology

The mumps virus is transmitted by respiratory droplets. It has an incubation period of 14-25 days after which time prodromal symptoms occur and last anywhere from 3-5 days. After the prodrome, the symptoms of the virus depend on which organ is affected. The most common presentation is a parotitis, which occurs in 30-40% of patients. Other reported sites of infection are the testes, pancreas, eyes, ovaries, central nervous system, joints, and kidneys. A patient is considered infectious from about 3 days before the onset and up to 4 days after the start of active parotitis. Infections can be asymptomatic in up to 20% of persons.

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Epidemiology

United States

Prior to the vaccine about 50% of children contracted mumps. Approximately 200,000 cases were reported in 1964 before the introduction of the vaccine compared with 291 cases in 2005. A resurgence occurred in 1986 and 1987, with almost 13,000 cases reported, and it was associated with a lack of state requirements for immunizations. These cases were mostly in older school-aged children (10-19 y). In the 1990s, 30-40% of cases reported each year were in persons aged 15 years or older as opposed to 90% being younger than 15 years old in earlier years. [6]

A recent outbreak of mumps occurred in Iowa, with 219 cases reported in 2006. In addition, another 14 cases of people with symptoms consistent with the virus were reported in nearby states (Illinois, Nebraska, and Minnesota). This is the largest number of cases reported in the United States since 1988. The median age of the 219 persons was 21 years, with 30% being college students. In 1991, Iowa mandated that 2 doses of mumps vaccine be required for all people entering public schools. Vaccination history was studied in 133 people from this outbreak: 65% (87) of the patients had received 2 doses, 14% (19) had received only 1 dose, and 6% (8) received no vaccine at all. [7]

Amongst the infected, the most commonly reported symptoms were parotitis (83%), submaxillary/submandibular gland swelling (40%), fever (36%), and sore throat (32%). The average length of illness was 5.1 days. Complications, including encephalitis and orchitis, were reported in 5% of patients. The source of the Iowa epidemic is unknown. [7]

International

The variations in the number of persons who receive the mumps vaccination worldwide make it difficult to estimate the numbers affected. The incidence varies markedly from region to region.

The United Kingdom reported an epidemic of mumps in 2005, with 56,390 cases reported in persons aged 15-24 years who were not vaccinated. [6]

Sex

For parotitis, males and females are affected equally.

Symptomatic meningitis has a male-to-female ratio of 3:1.

Age

Before the mumps vaccine was introduced, most cases were in children aged 5-9 years, with 90% being younger than 15 years. The resurgence in the late 1980s affected older children aged 10-19 years. In more recent years, up to 30-40% of cases have been in persons older than 15 years. [1]

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Prognosis

Prognosis for mumps infection is usually good.

The most serious complication is encephalitis, with a mortality rate of 1.4%.

Unilateral orchitis rarely causes sterility; however bilateral orchitis carries an increased risk.

Unilateral sensorineural hearing loss is believed to be a rare complication; however, subclinical or unrecognized mumps may contribute toward a higher incidence of unilateral hearing loss in childhood than is currently known. Bilateral involvement has also been documented.

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Patient Education

For excellent patient education resources, visit eMedicine's Bacterial and Viral Infections Center. Also, see eMedicine's patient education article Mumps.

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Mortality/Morbidity

Between 1980 and 1999, an average of one death per year has occurred due to mumps. Most deaths occur in persons older than 19 years.

CNS involvement is common, but symptomatic meningitis only occurs in about 15% of patients. It usually resolves without complications, but adults are at a higher risk for sequelae. Encephalitis is rare and is seen in fewer than 2 per 100,000 cases. It has a mortality rate of 1.4%. [8, 9, 10, 11]

Orchitis (usually unilateral) occurs in 50% of postpubertal males. It causes testicular atrophy in as many as 50% of persons affected but rarely causes sterility. The risk of sterility is higher in bilateral orchitis. [9, 12] Oophoritis occurs in a small percentage of postpubertal girls.

Pancreatitis occurs in 5% of persons infected with mumps. The hyperglycemia that results is usually transient, but a few cases of diabetes mellitus have been reported. It is not conclusive that the mumps virus has been the definitive cause. [9]

Deafness has been reported in 1 per 20,000 cases of mumps. In 80% of cases, the hearing loss is reported to be unilateral. [13, 14]

Some deaths due to myocarditis have been reported. The incidence of this complication is reported to be up to 15%, but it is usually asymptomatic. [15]

The risk of spontaneous abortion is increased in women with mumps during the first trimester of pregnancy. Mumps during pregnancy has not been associated with congenital malformations. [16]

Other reported complications include chronic arthritis, arthralgias, and nephritis. [15]

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Causes

Mumps is typically caused by a single-stranded RNA virus belonging to the Paramyxovirus genus. Humans serve as the only natural host for the mumps virus.

Other viruses implicated in recurrent parotitis are influenza, echovirus, parainfluenza (types 1 and 3), and coxsackievirus A. More rare causes of parotitis seen in persons with HIV infection are adenovirus or cytomegalovirus.

Risk factors include lack of immunization or incomplete immunization, international travel, and immune deficiencies.

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