eMedicine Specialties > Pediatrics: General Medicine > Infectious Disease

Mumps

Author: Cem S Demirci, MD, Fellow in Endocrinology, Children's Hospital of Pittsburgh
Coauthor(s): Walid Abuhammour, MD, FAAP, Associate Professor of Pediatrics, Michigan State University; Director of Pediatric Infectious Disease, Department of Pediatrics, Hurley Medical Center
Contributor Information and Disclosures

Updated: Nov 20, 2009

Introduction

Background

Mumps is a single-stranded RNA virus and a member of the family Paramyxoviridae, genus Paramyxovirus. It has 2 major surface glycoproteins: the hemagglutinin-neuraminidase and the fusion protein. Mumps virus is sensitive to heat and ultraviolet light.

Mumps vaccine was licensed in the United States in December 1967, and the Advisory Committee on Immunization Practices (ACIP) recommended that its use be considered for children approaching puberty, for adolescents, and for adults. At that time, the public health community considered mumps control a low priority, and the ACIP stated that mumps immunization should not compromise the effectiveness of established public health programs. However, in 1972, the ACIP recommendations were strengthened to indicate that mumps vaccination was particularly important for the initially targeted age groups; in 1977, the ACIP recommended the routine vaccination of all children aged 12 months or older.

The use of mumps vaccine in young children was facilitated by the introduction (in 1977) and extensive use of the measles-mumps-rubella (MMR) vaccine. In 1980, stronger recommendations called for the vaccination of susceptible children, adolescents, and adults, unless such vaccination was contraindicated. Following these increasingly comprehensive recommendations and the enactment of state laws requiring mumps vaccination for school entry and attendance, the reported incidence of mumps steadily declined. However, during 1986 and 1987, large outbreaks occurred among underimmunized cohorts of persons born during 1967-1977, resulting in a shift in peak incidence from persons aged 5-9 years to persons aged 10-19 years.¹ In 1989, the ACIP recommended that a second dose of measles-containing vaccine be administered to children aged 4-6 years (at time of entry to kindergarten or first grade) and designated MMR as the vaccine of choice.^1,2

The incidence of mumps during 1988-1998 decreased among all age groups. The greatest decrease occurred among persons aged 10-19 years, which was the same age group in which the greatest increases had occurred during 1986 and 1987, when a resurgence of outbreaks occurred among susceptible adolescents and young adults. Subsequent outbreaks have occurred among highly vaccinated populations. During 1989-1990, a large outbreak occurred among students in a primary and a secondary school; most of the students in these schools had been vaccinated, suggesting that vaccination failure, in addition to failure to vaccinate, might have contributed to the outbreak. In 1991, another outbreak occurred in a secondary school where most of the students had been vaccinated; this outbreak was also mostly attributed to primary vaccination failure.

The shift in higher risk for mumps to these other age groups (ie, from younger children of school ages to older children, adolescents, and young adults), which occurred after the routine use of the mumps vaccine was initiated, has persisted despite minimal fluctuations in disease incidence that occurred in recent years among the various age groups.

Pathophysiology

Mumps virus produces a generalized infection. After entry into the oropharynx, viral replication occurs, causing subsequent viremia and involving glands or nervous tissue.

Frequency

United States

After the licensure of the mumps vaccine in the United States in December 1967 and the subsequent introduction of state immunization laws in an increasing number of states, reported incidence of mumps substantially decreased. The 666 cases of mumps reported in 1998 reflect a 99% decrease from the 152,209 cases reported for 1968. Although incidence decreased in all age groups, the largest decreases (>50% reduction in incidence rate per 100,000 population) occurred in persons aged 10 years or older. Overall, the incidence of mumps was lowest in states with comprehensive school immunization laws requiring mumps vaccination and was highest in states without such requirements.

The prevalence of mumps is at record low levels because of the recommendation of 2 doses of MMR vaccine and its high coverage rate in the United States. During the 1990s, mumps cases substantially declined, from 5,292 reported cases in 1990 to 266 reported cases in 2001, meeting the Healthy People 2000 objective of less than 500 cases per year. In 2003, the Centers for Disease Control and Prevention (CDC) reported a total of 231 cases.³

However, on July 26, 2005, an epidemic occurred in Sullivan County, New York at a summer camp.⁴ An investigation conducted by the New York State Department of Health (NYSDOH) identified 31 cases of mumps, likely introduced by a camp counselor who had traveled from the United Kingdom and had not been vaccinated for mumps. Even in a population with 96% vaccination coverage, as was the case with participants in the summer camp, a mumps outbreak can result from exposure to virus imported from a country with an ongoing mumps epidemic. The likelihood of disease in US residents caused by imported virus from areas with mumps epidemics remains high.

International

Because the virus is present throughout the world, risk of exposure to mumps outside the United States may be high. Mumps remains endemic in many countries throughout the world, and mumps vaccine is used in only 57% of countries that belong to the World Health Organization, predominantly in countries with more developed economies.⁵ In England and Wales, an epidemic of mumps began in 2005, with 56,390 notified cases reported.⁶

Mortality/Morbidity

Death due to mumps is rare; more than half of the fatalities occur in persons older than 19 years.

Mumps encephalitis occurrence ranges as high as 5 cases per 1000 reported mumps cases, and males are affected 3-5 times more frequently than females. Permanent sequelae are rare, but the reported encephalitis case-fatality rate has averaged 1.4%.

Approximately 10% of all infected patients develop a mild form of meningitis, which could be confused with bacterial meningitis. Encephalitis, transient myelitis, or polyneuritis is rare. Unilateral hearing loss is associated with mumps infection but is also rare.

Orchitis occurs in 10-20% of patients; subsequent sterility is rare. Oophoritis is quite rare and is usually a benign inflammation of the ovaries. Other rare complications include myocarditis, nephritis, arthritis, thyroiditis, pancreatitis, thrombocytopenia purpura, mastitis, and pneumonia. These usually resolve within 2-3 weeks without sequelae.

Race

During 1990-1998, race and ethnicity were reported for approximately two thirds of cases in each of 28 states and the District of Columbia. Mumps incidence decreased for people of all races during this 4-year period. For each year, incidence was highest among black persons, ranging from 1.2-8.2 times the incidence of any other racial group. In people of every age group, incidence rates for black persons exceeded rates for people of other racial groups; this relationship was most notable for persons aged 5-19 years.

Although incidence rates for Hispanics exceeded the rates for non-Hispanics in every age group, differences in rates were minimal for children younger than 5 years and for persons aged 20 years or older. The greatest difference in incidence rates between Hispanics and non-Hispanics was in persons aged 5-19 years.

Sex

No sexual predilection is observed.

Age

As in the prevaccine era, most reported mumps cases still occur in school-aged children (aged 5-14 y). Almost 60% of reported cases occurred in this population from 1985-1987, compared with an average of 75% of reported cases from 1967-1971, the first 5-year period postlicensure. However, for the first time since mumps became a reportable disease, the reported peak incidence rate shifted from children aged 5-9 years to older age groups for 2 consecutive years (ie, 1986, 1987).

Persons aged 15 years or older accounted for more than one third of the reported total from 1985-1987, whereas during the period 1967-1971, an average of only 8% of reported cases occurred among this population. Although reported mumps incidence increased in all age groups from 1985-1987, the most dramatic increases were among adolescents aged 10-14 years (almost a 7-fold increase) and young adults aged 15-19 years (more than an 8-fold increase).

Increased occurrence of mumps in susceptible adolescents and young adults has been demonstrated in several recent outbreaks in high schools, on college campuses, and in occupational settings.⁷ Nonetheless, despite this age shift in reported mumps, the overall reported risk of disease in persons aged 10-14 and those aged 15 years or older is still lower than that in the prevaccine and early postvaccine era.

Clinical

History

The incubation period is 14-21 days, and mumps is communicable from 6 days before to 9 days after facial swelling is apparent. However, 30% of infections are subclinical.

• Symptoms in the history mostly consist of fever, headache, and malaise. Within 24 hours, patients report an ear pain localized near the lobe of the ear and aggravated by a chewing movement of the jaw. The fever usually subsides after a variable period of as long as 1 week, well before the salivary gland edema disappears.
• Older children may describe a sensation of swelling at the angle of the jaw in the early stage, especially with a sour taste.

Physical

After the prodromal period, one or both parotid glands begin to enlarge; 70-80% of cases are bilateral. Edema over the parotid gland typically occurs with nondiscrete borders, pain with pressure, and obscured angle of the mandible. A recent study investigated the difficulty in definitive mumps diagnosis, noting that only 14% of 2082 cases during an outbreak were laboratory confirmed.⁸ The conclusion was that the clinical acumen for mumps diagnosis based solely on clinical presentation is low.

• Parotitis: The classic illness of mumps consists of swelling of the parotid gland (ie, parotitis, parotiditis). However, mumps is no longer the most common cause of parotitis. Systemic symptoms include low-grade fever, headache, malaise, anorexia, and abdominal pain. Acid-containing foods may aggravate discomfort of the parotid gland. Ordinarily, the parotid gland is not palpable, but in patients with mumps, it rapidly progresses to maximum swelling over several days. Unilateral swelling usually occurs first, followed by bilateral parotid involvement. Occasionally, simultaneous involvement of both parotid glands occurs. Unilateral parotid disease occurs in fewer than 25% of patients. Fever subsides within 1 week and disappears before swelling of the parotid gland resolves, which may require as long as 10 days. Other salivary glands may be involved, including both submaxillary glands and sublingual glands, and orifices of the ducts may be erythematous and edematous.
• Orchitis: Approximately one third of postpubertal male patients develop unilateral orchitis. It usually follows parotitis but may precede parotitis or occur in the absence of parotitis. Usually, it appears in the first week of parotitis, but it can occur in the second or third week. Bilateral orchitis occurs much less frequently, and although gonadal atrophy may follow orchitis, sterility is rare even with bilateral involvement. Prepubertal boys may develop orchitis, but it is uncommon in those younger than 10 years. Orchitis is accompanied by high fever, severe pain, and swelling. Nausea, vomiting, and abdominal pain are not uncommon. Fever and gonadal swelling usually resolve in 1 week, but tenderness may persist.
• Meningoencephalitis
  • CNS involvement with mumps is not uncommon, and it occurs more often as meningitis rather than true encephalitis. It may precede parotitis or appear in the absence of parotitis but usually occurs in the first week after parotitis. Headache, fever, nausea, vomiting, and meningismus are common. Marked changes in sensorium and convulsions are not usual. Pleocytosis of the CSF occurs in a high percentage of persons without clinical evidence of central nervous system involvement.
  • In clinically diagnosed meningoencephalitis, a CSF mononuclear pleocytosis occurs, as does normal glucose, although hypoglycorrhachia has been reported. The mumps virus may be isolated from CSF early in the illness. Mumps meningoencephalitis carries a good prognosis and is usually associated with an uneventful recovery. Other clinical manifestations of mumps include pancreatitis accompanied by severe abdominal pain, chills, fever, and persistent vomiting. Thyroiditis, oophoritis, and mastitis occasionally occur.
• Deafness: Neuritis of the auditory nerve may result in deafness. Sudden onset of tinnitus, ataxia, and vomiting is followed by permanent deafness. Other neurologic complications include facial nerve neuritis and myelitis.
• Other complications: Less common complications include arthritis, myocarditis, and hematologic complications.

Causes

• Lack of immunization, international travel, and immune deficiencies can make a child more prone to infection by Paramyxovirus mumps virus.

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