MUMPS : CLINICAL ASPECTS
After an incubation period of 12 to 29 days (average, 16 to 18 days), the typical case is characterized by fever and swelling with tenderness of the salivary glands, especially the parotid glands. Swelling may be unilateral or bilateral and persists for 7 to 10 days. Several complications can occur, usually within 1 to 3 weeks of onset of illness. All appear to be a direct result of virus spread to other sites and illustrate the extensive tissue tropism of mumps.
Complications, which can occur without parotitis, include infection of the following:
1. Meninges: Approximately 10% of all infected patients develop meningitis. It is usu-ally mild, but can be confused with bacterial meningitis. In about one third of these cases, associated or preceding evidence of parotitis is absent.
2. Brain: Encephalitis is occasionally severe.
3. Spinal cord and peripheral nerves: Transverse myelitis and polyneuritis are rare.
4. Pancreas: Pancreatitis is suggested by abdominal pain and vomiting.
5. Testes: Orchitis is estimated to occur in 10 to 20% of infected men. Although subse-quent sterility is a concern, it appears that this outcome is quite rare.
6. Ovaries: Oophoritis is an unusual, usually benign inflammation of the ovarian glands.
Other rare and transient complications include myocarditis, nephritis, arthritis, thy-roiditis, thrombocytopenic purpura, mastitis, and pneumonia. Most complications usually resolve without sequelae within 2 to 3 weeks. However, occasional permanent effects have been noted, particularly in cases of severe CNS infection, in which sensorineural hearing loss and other impairment can occur.
Mumps virus can be readily isolated early in the illness from the saliva, pharynx, and other affected sites, such as the cerebrospinal fluid (CSF). The urine is also an excellent source for virus isolation. Mumps virus grows well in primary monolayer cell cultures derived from monkey kidney, producing syncytial giant cells and viral hemagglutinin. Rapid diag-nosis can be made by direct detection of viral antigen in pharyngeal cells or urine sediment.
The usual serologic tests are enzyme immunoassay (EIA) and indirect immunofluores-cence to detect IgM- and IgG-specific antibody responses. Other serologic tests are also available, such as complement fixation, hemagglutination inhibition, and neutralization. Of these, the neutralization test is the most sensitive for detection of immunity to infection.
No specific therapy is available. Since 1967, a live attenuated vaccine that is safe and highly effective has been available. As a result of its routine use, infections in the United States are now exceedingly rare. The vaccine is produced by serial propagation of virus in chick embryo cell cultures. It is commonly combined with measles and rubella vaccines (MMR) and given as a single injection at 12 to 15 months of age. A second dose of MMR is recommended at 4 to 6 years of age; those who have missed the second dose should re-ceive it no later than 11 to 12 years of age. A single dose causes seroconversion in more than 95% of recipients. Duration of immunity, especially if the two-dose regimen is fol-lowed, appears to be more than 25 years and may be lifelong.