Pediatrics

Mumps

OVERVIEW: What every practitioner needs to know

Are you sure your patient has mumps? What are the typical findings for this disease?

Mumps is an acute viral infection usually seen in childhood. It is characterized typically by unilateral or bilateral swelling of the salivary glands (usually parotid) proceeded for 1-2 days by headache and loss of appetite. Bilateral swelling is present in approximately 70% of infected children. Approximately one third of infected children have no salivary gland involvement.

Symptoms of respiratory tract infection may be present. Physical examination typically reveals swelling of the parotid area with upward and outward displacement of the earlobe. The angle of the mandible is obscured by the swollen parotid gland. The opening of Stensen duct is edematous and erythematous. The child will likely complain of pain when eating or drinking acidic foods. Accompanying findings may include edema of the presternal tissue and orchitis in post-pubertal males.

Possible complications

Orchitis is uncommon in prepubertal males, but it complicates mumps in approximately one third of post-pubertal teens, with the highest incidence in those over 15 years of age. Affected boys develop fever, lower abdominal pain, and testicular pain 4 to 8 days following onset of parotid involvement. Involvement is most often unilateral, and infertility is uncommon, though approximately 50% may have some testicular atrophy.

Mumps virus has affinity for the CNS, and approximately 50% of infected individuals will have CSF pleocytosis, but <10% have clinical evidence of meningitis and <1% develop encephalitis. Rare complications may include arthritis, glomerulonephritis, myocarditis, pancreatitis, thyroiditis, cerebellar ataxia, transverse myelitis, ascending polyradiculitis, oophoritis, thrombocytopenia (including thrombocytopenic purpura), endocardial fibroelastosis, and hearing impairment.

What other disease/condition shares some of these symptoms?

Parotid gland inflammation and swelling can be caused by other viruses, including influenza, enteroviruses, parainfluenza, cytomegalovirus, lymphocytic choriomeningitis virus, and human immunodeficiency virus. Bacterial infection of the parotid gland, usually caused by Staphylococcus aureus, may result from hematogenous spread or from ascending infection of the oropharyngeal flora. Salivary duct stones, ingestion of starch, and metabolic disorders, such as diabetes mellitus, cirrhosis, and malnutrition, can all lead to parotitis; and some drugs (e.g., phenylbutazone, thiouracil, and iodides) have been implicated.

What caused this disease to develop at this time?

Mumps virus is transmitted through respiratory secretions. The period between infection and development of symptoms (incubation period) is typically 16 to 18 days, but may be as short as 12 days or as long as 25. The period of greatest communicability is 1-2 days prior to the onset of parotid swelling, but virus has been isolated from saliva as early as 9 days before symptoms appear.

What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?

The WBC count is usually low or within the normal range with a relative lymphocytosis. Serum amylase may be elevated during the first week of illness.

The diagnosis of mumps can be confirmed by isolation of the virus from a swab of Stenson duct exudate, throat washing, saliva, or spinal fluid or by detection of the virus using reverse transcription polymerase chain reaction. Virus may be present in saliva as early as a week before symptoms appear and up to 9 days of illness.

Detection of virus-specific IgM or a significant rise in IgG titers from sera collected during the acute illness and again in convalescence also confirms the diagnosis, though a delayed rise in IgM antibody may necessitate a repeat determination 2-3 weeks after onset of symptoms. Antibody test results may be difficult to interpret in previously immunized individuals, and mumps virus may be shed for only a few days in such individuals; attempts at detection of the virus should be undertaken in the first 1-3 days following onset of symptoms.

Would imaging studies be helpful? If so, which ones?

Imaging studies are not needed to diagnose mumps.

Confirming the diagnosis

Mumps should be suspected in any patient who has acute unilateral or bilateral swelling of the parotid or other salivary glands for more than 2 days without apparent alternative explanation. Laboratory confirmation should be attempted in such patients. Cases of mumps should be reported to public health authorities through the National Notifiable Diseases Surveillance System.

If you are able to confirm that the patient has mumps, what treatment should be initiated?

There is no specific treatment for mumps. Supportive treatment involves hydration and avoidance of acidic foods.

What are the possible outcomes of mumps?

The symptoms of mumps usually resolve without complication in 3 to 5 days.

In cases with central nervous system involvement (meningitis or encephalitis), the infection is usually self-limited, but complications may include ataxia, behavioral problems, aquaductal stenosis with hydrocephalus, paralysis, neuroretinitis, and sensorineural hearing loss. Encephalitis may result in death in approximately 1% of patients.

Infertility is an uncommon complication in boys who develop orchitis due to mumps, even when involvement is bilateral.

Joint involvement as a complication of mumps is more likely in males than in females. The large joints are typically affected, and symptoms may persist for as long as 6 months with complete resolution.

Other complications as mentioned above are rare.

Infection during the first trimester of pregnancy has been associated with spontaneous abortion, though there is no demonstrated risk of congenital anomalies to infants born following maternal infection. Endocardial fibroelastosis in newborns has been associated with maternal mumps during pregnancy, and mumps virus has been detected by PCR in infants who have died from endocardial fibroelastosis.

What causes this disease and how frequent is it?

Mumps is caused by mumps virus, a member of the genus Rubulavirus in the Paramyxoviridae family. It is an RNA virus which is transmitted through respiratory secretions. Viral replication occurs in the nasopharynx and lymph nodes and is followed by viremia and spread to multiple organs, including the CNS and epithelium of salivary glands.

Before the availability of mumps vaccine, mumps was a common infection in children < 10 years of age, and annual outbreaks were seen typically between January and May. Mumps vaccine has been recommended for use in all children in the United States since 1977, and the 2-dose regimen was recommended in 1989. Since then the incidence of mumps in children in the United States has fallen dramatically, to less than 300 cases per year, and the previous seasonal peak is no longer seen. Outbreaks have occurred in recent years, however, among older adolescents and young adults, many of whom had received the recommended immunizations.

How do these pathogens/genes/exposures cause the disease?

Mumps virus invades through hematogenous spread following initial infection of the nasopharyngeal mucosa and regional lymph nodes. Pathologic changes of the salivary glands include edema and infiltration of lymphocytes and macrophages. Distal organ involvement is a result of direct viral infection with inflammatory changes similar to those seen in the salivary glands.

What complications might you expect from the disease or treatment of the disease?

Complications are discussed above. There is no specific therapy available.

How can mumps be prevented?

The incidence of mumps in the United States and in other developed countries has been markedly reduced by the use of live, attenuated mumps vaccine and the implementation of the recommended two-dose regimen prior to school entry. The first dose, given as combined measles, mumps, and rubella vaccine, is recommended at 12-15 months of age, and the second dose is recommended at 4-6 years of age.

Vaccine administration has not been demonstrated to reduce the likelihood of acquiring infection following exposure, though administration during the incubation period poses no risk. One dose of vaccine results in approximately 80% likelihood of protection, while two doses protects 88-95% of recipients. The duration of protection is not known with certainty.

Adverse reactions to mumps vaccine are rare but can include orchitis, parotitis, and fever.

What is the evidence?

"Centers for Disease Control and Prevention. Updated recommendations of the Advisory Committee on Immunization Practices (ACIP) for the control and elimination of mumps". MMWR. vol. 55. 2006. pp. 366-368.

(This resource provides updated recommendations for the use of mumps vaccine following an outbreak involving individuals in 11 states.)

Sullivan, KM, Halpin, TJ, Kim-Farley, R. "Mumps disease and its health impact: an outbreak-based report". Pediatrics. vol. 76. 1985. pp. 533.

(Description of a mumps outbreak in a middle school in Ohio in 1981.)

Pickering, LK, Baker, CJ, Kimberlin, DW, Long, SS. "American Academy of Pediatrics. Mumps". Report of the Committee on Infectious Diseases. American Academy of Pediatrics. 2012. pp. 514-518.

(A brief overview of the clinical illness, diagnostic methods, and prevention.)

McLean, HQ, Fiebelkorn, AP, Tempte, JL. "Prevention of measles, rubella, congenital rubella syndrome, and mumps, 2013: summary recommendations of the Advisory Committee on Immunization Practices (ACIP)". MMWR. vol. 62. 2013. pp. 1-34.

(This report presents the recent revisions adopted by the Advisory Committee on Immunization Practices [ACIP] on October 24, 2012, and summarizes all existing ACIP recommendations published during 1998–2011.)
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