Mumps

Dennis L. Murray

Mumps is a communicable systemic viral illness usually characterized by parotitis. With the widespread use of mumps vaccine, the disease has become less common. A significant number of infections are asymptomatic.

EPIDEMIOLOGY

Humans are the only known natural hosts of mumps virus. Mumps virus infections are spread by respiratory droplet or by direct contact with infected saliva. Virus can be demonstrated in respiratory secretions up to 7 days before through 9 days after the onset of parotitis.² The normal incubation period is from 16 to 18 days (range 12–25 days). In susceptible, unimmunized populations, 60% to 70% of infections are associated with parotitis.⁴ However, there is a substantial subclinical attack rate produced by the mumps virus. Approximately 20% of mumps infections may go unrecognized, especially in adults, because they do not have evidence of parotitis.^2,5 Given the number of subclinical cases, information regarding a patient’s history of mumps infection is notoriously inaccurate. Mumps virus infection is most communicable from 1 to 2 days prior to parotid swelling until 5 days after parotid swelling begins.²

Introduction of an effective, live-attenuated virus vaccine (Jeryl Lynn strain) in 1967, combined with the introduction of school laws regarding mumps vaccination, led to a marked reduction in the number of reported cases of mumps in the United States, from more than 185,000 cases in 1968 to 2982 in 1985.⁷ Following a brief resurgence of disease, a revised recommendation for two doses of measles-mumps-rubella (MMR) vaccine in 1989⁴ and subsequent changes in school laws requiring two doses of vaccine, the annual number of mumps cases further declined. From 2001 to 2005, fewer than 300 cases of mumps were reported annually in the United States.⁸ In 2006, a multistate mumps outbreak with more than 5700 cases, many involving older adolescents and young adults, demonstrated that although two doses of vaccine were more protective than a single dose, protection from infection, even with two doses of vaccine, was not 100%.^5,9 Outside the United States, mumps remains endemic in many countries throughout the world.^10,11 In 2005, only 57% of World Health Organization member-countries reportedly used mumps vaccine.¹¹

A single attack of mumps is believed to confer permanent immunity against a subsequent attack, regardless of whether the patient had evidence of parotitis. Mumps antibody is transferred across the placenta and persists during the first several months of the infant’s life.

PATHOPHYSIOLOGY

Mumps is caused by a paramyxovirus, which is closely related antigenically to parainfluenza virus. Virons are approximately 150 nm and contain RNA. Mumps virus can be propagated in a variety of cell cultures and in embryonated eggs. Mumps virus produces a generalized, systemic infection. Although parotid involvement has been emphasized, mumps can definitely occur without parotid swelling. Meningitis and renal involvement may be considered part of the disease. A majority (50–60%) of infected persons have cerebrospinal fluid (CSF) pleocytosis, even in the absence of clinical signs of meningitis. Adults, and males, are at greater risk of developing meningitis than are children.^2,7 Viruria occurs frequently in cases of uncomplicated mumps; hematuria and proteinuria may occur, and abnormalities of renal function have been reported. Although orchitis is a known complication of postpubertal males and may lead to some degree of testicular atrophy, sterility is rare.^16,17 Oophoritis is relatively uncommon (5%) in postpubertal females. Other organs may be involved infrequently. Death due to mumps virus is rare; fatalities are more frequent in those older than 19 years. In such rare patients, virus has been recovered from multiple organs at autopsy.

CLINICAL MANIFESTATIONS

A patient with mumps rarely has severe systemic manifestations. Temperatures are only moderately elevated, usually for 3 to 4 days. Symptoms such as headache, anorexia, and abdominal discomfort may precede parotid swelling by 1 to 2 days. Parotid swelling may be the first sign of illness; swelling may last 7 to 10 days and be observed on one or both sides (Fig. 318-1). Two or 3 days after the onset of swelling on one side, the opposite side may become involved. The submandibular glands may swell along with or in the absence of parotid swelling. Presternal edema is sometimes present.

The entire parotid gland is swollen, including the uncinate lobe, which extends under the back of the ear lobe. The borders of the gland are usually not discrete. Pressure on the parotid gland causes pain, and trismus (spasm of the masticator muscles) may occur.

Parotid swelling produces a fair amount of discomfort. Eating or drinking acidic foods, such as orange juice, is said to elicit much discomfort. Inflammation of the orifice of the Stenson duct may or may not be present.

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