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Pediatrics, Mumps

Author: Eileen C Quintana, MD, Assistant Professor, Departments of Pediatrics and Emergency Medicine, St Christopher's Hospital for Children
Coauthor(s): Hosseinali Shahidi, MD, MPH, Assistant Professor, Departments of Emergency Medicine and Pediatrics, State University of New York and Health Science Center at Brooklyn
Contributor Information and Disclosures

Updated: Jul 9, 2009

Introduction

Background

The mumps virus is a paramyxovirus that shares various epidemiological characteristics with other well-known viral pediatric diseases, such as measles and rubella. The disease is distributed worldwide, and paramyxovirus is highly infectious to nonimmune individuals.

During the 2003 epidemic of severe acute respiratory syndrome (SARS), it was thought that the SARS-causing virus belonged to the Paramyxoviridae family. However, current case criteria have determined that SARS follows the clinical, laboratory, and transmission characteristics of a coronavirus named SARS-associated coronavirus (SARS-CoV) and not specifically to the mumps virus.^1,2

Humans are the sole reservoir for the mumps virus, and the transmission mode is person to person via respiratory droplets and saliva.

Mumps is caused by a specific virus with only one antigenic type known. It contains a single-stranded, negative-sense RNA surrounded by an envelope. One of the 2 glycoproteins on the surface of the envelope mediates neuraminidase and hemagglutinating activity, whereas the other is responsible for lipid membrane fusion to the host cell.

Even though it shares morphologic features of parainfluenza virus type 2, no cross-immunity between the 2 viruses is apparent.

Pathophysiology

After the initial entry into the respiratory system, the virus replicates locally, then follows with a viremic dissemination to target tissues, such as the central nervous system (CNS) and salivary glands, particularly the parotid glands. This fact was a significant contribution from an experimentally induced mumps infection by Henly et al in 1948.

A secondary phase of viremia, found before the immune response, is the result of replication of the virus at the target organs. Viruria is common, via blood transmission of the virus into the kidneys, where active replication occurs. Therefore, impairment of renal function may occur.

Cell necrosis and inflammation with mononuclear cell infiltration is the tissue response. Salivary glands show edema and desquamation of necrotic epithelial cell lining the ducts. Focal hemorrhage and destruction of germinal epithelium may occur, leading to duct plugging.

Frequency

United States

The incidence of mumps, which is more common in the winter and spring, has markedly declined since the introduction of the mumps vaccine. In 1967, when the live-attenuated mumps virus vaccine was introduced in the United States, 185,691 cases occurred. While a minor resurgence of mumps occurred from 1986-1987, in 1991, 4000 cases were reported.³ Generally, the incidence is between 500-1500 yearly; however, another mumps resurgence has been noted in the central United States in 2006. This resurgence in a single year has occurred in college students aged 18-25 years.⁴

Mortality/Morbidity

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

Unilateral hearing loss is associated with mumps infection. This devastating complication is rare.

For those who develop meningoencephalitis, the mortality rate is 2%.⁵

• 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.
• Orchitis occurs in 10-20% of patients. Subsequent sterility is rare, and 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.

Sex

• No sex predilection exists.
• For meningoencephalitis, males are affected 3-5 times more often than females.

Age

Incidence rates are currently highest in those aged 5-9 years, followed by those aged 1-4 years, then those aged 10-14 years.

Clinical

History

• The incubation period of mumps virus is an average of 16-18 days (in approximately 30-40% of patients), with a range of 12-29 days.
• The period of communicability is usually from 9 days prior to the onset of parotid edema to 1-2 days after onset of swelling and occasionally lasting as long as 7 days after swelling.
• Symptoms include fever, headache, and malaise.
• Within 24 hours, patients usually complain of ear pain, which is localized near the lobe of the ear and aggravated by a chewing movement of the jaw.
• Fever usually subsides after a variable period of up to 1 week and well before the salivary gland edema disappears.

Physical

• The clinical manifestations appear to be a direct result of virus spread to other sites, which illustrates the extensive tissue tropism of mumps.
• After the initial presentation of fever, headache, and earache, the parotid gland enlarges and rapidly progresses to maximum size in 1-3 days.
  • As the edema progresses, the lobe of the ear is displaced upward and outward.
  • Pain and tenderness may be intense during this period, and symptoms rapidly subside after swelling reaches its peak. The parotid gland gradually decreases in size in 3-7 days. Commonly, one parotid gland swells before the other. Only 25% of patients with mumps have bilateral parotitis. Stensen duct opening may be erythematous and edematous.
  • Sublingual gland involvement, most commonly bilateral, is considered the least common manifestation of mumps. The sublingual gland is palpated on the floor of the mouth and submental area. In severe and extensive cases, the edema may extend to the presternal area due to an obstruction of the lymphatic vessels by the compression of the enlarged salivary glands.
  • Submaxillary gland edema, palpable underneath and anterior to the angle of the mandible, may be accompanied by edema spreading onto the cheek and downward onto the neck. If parotitis does not simultaneously occur, it is difficult to differentiate from cervical adenitis. Wharton duct opening may be erythematous and edematous.
• Epididymo-orchitis is the second most common manifestation of adult mumps, which is usually preceded by parotitis. Unilateral involvement is found in 20-30% of the patients, whereas bilateral involvement occurs in fewer than 2% of cases.⁶
  • Orchitis presents acutely with fever, chills, nausea, vomiting, and lower abdominal pain. After the fever, the testes begin to rapidly swell. The size increase could be slight or as much as 4 times normal size. As the fever decreases, the pain and edema subside. Loss of turgor is noticed with as many as 50% of cases demonstrating atrophy. Absolute sterility sequela is rare, with impairment of fertility found in 13% of patients.
  • Oophoritis is associated with pelvic pain and tenderness. It is noted in 7% of postpubertal females. Impairment of fertility is not evident.
• Meningoencephalitis is the most frequent complication in childhood. The true incidence is difficult to determine because of the subclinical infection of the CNS, but clinical findings have been reported in as many as 10% of cases. The mortality rate is 2%, with males being affected 3-5 times more often than females.
  • The pathogenesis is described as a primary infection of the neurons and/or postinfection encephalitis with demyelination.
  • Parotitis may appear simultaneously with the primary neuron infection, or it may appear 10 days after the parotitis in the postinfection type.
  • The illness presents with fever, headache, nausea, vomiting, nuchal rigidity, and change of sensorium. Mumps is a common cause of aseptic meningitis, which usually is indistinguishable from other causes, such as enteroviruses and herpes or pox viruses. The cerebrospinal fluid (CSF) has less than 500 cells/mm³, mostly lymphocytes. Mumps virus can be isolated in the CSF.
• Pancreatitis is a severe but, fortunately, rare manifestation. A sudden onset of epigastric pain and tenderness occurs accompanied by fever, chills, nausea, and vomiting. Elevated amylase level is found with mumps regardless of the presence of pancreatitis. Lipase is a more specific indicator of pancreatic involvement, and measurements of it should be obtained. After 1 week, the patient generally completely recovers.
• A diffuse tender swelling of the thyroid gland may occur about 1 week after parotitis, with the development of antithyroid antibodies.
• Myocarditis is a serious and extremely rare manifestation. The only reported ECG findings are depression of ST segments and bradycardia in 13% of adults with myocarditis.
• Mastitis is uncommon in either sex.
• Unilateral deafness, permanent or transient, has a low incidence (1:15,000), but mumps is the leading cause of deafness.⁷
• Ocular manifestations include dacryadenitis, optic neuritis, uveokeratitis, scleritis, and central vein thrombosis.
• Arthralgia is associated with erythema and edema of the joint; recovery is complete.
• Thrombocytopenia purpura may be present (infrequent).

Causes

Mumps is caused by a paramyxovirus that has one antigenic type. It contains a single-stranded, negative-sense RNA surrounded by an envelope.

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