DESCRIPTION

Centers for Disease Control and Prevention (CDC) clinical case definition for mumps: illness with acute onset of unilateral or bilateral, tender, self-limited swelling of the parotid or other salivary gland, lasting ≥2 days, without other apparent cause

EPIDEMIOLOGY

• In the prevaccine era, 90% of all children contracted mumps virus infection by 14 years of age.
• Incidence of this once very common disease has declined dramatically since the advent of universal childhood immunization.
• Outbreaks, however, continue to occur, and cases in the United States have ranged from several hundred to several thousand cases annually.
• Since 2014, >1,000 cases per year have been reported in the United States, with >6,000 cases reported in 2016.
• Most outbreaks have been linked to being in a close crowded environment and intense exposures, such as universities, sports teams, and close-knit religious communities.
• Outbreaks can occur in highly vaccinated communities, particularly in very close-contact settings such as college dormitories and camps.
• High vaccination rate helps limit the severity, size, and duration of mumps outbreaks.

GENERAL-PREVENTION

• Two combination mumps vaccine are used:
  • MMR: measles, mumps, rubella
  • MMRV: measles, mumps, rubella, varicella
• A single 0.5-mL SC injection of live mumps vaccine (MMR or MMRV) is recommended at 12 to 15 months.
• A second vaccination is recommended between 4 and 6 years of age.
• The efficacy of 2 doses of vaccines is estimated at approximately 80–90%.
• Primary vaccine failure and waning vaccine-induced immunity have been reported.
• During mumps outbreaks, a third dose of vaccine may be recommended by public health authorities for targeted populations in conjunction with CDC guidance. Studies indicate no increase in adverse effects after a third vaccine dose and improved control of mumps outbreak.
• The first dose of MMR vaccine can be associated with fever and rash:
  • These symptoms occur 7 to 12 days after immunization.
  • Measles component is usually the culprit.
• Both MMRV and MMR vaccines, but not varicella vaccine alone, are associated with increased outpatient fever visits and seizures 5 to 12 days after vaccination in 12- to 23-month-olds, with MMRV vaccine increasing fever and seizure twice as much as the MMR + varicella vaccine.
• Vaccine should not be administered to children who are immunocompromised by disease or pharmacotherapy, as well as to pregnant women.
• If a child has recently received immune globulin (IG), administration of MMR vaccine should be delayed (for 3 to 11 months depending on the dose of immune globulin).
• Children with HIV infection who are not severely immunocompromised (age-specific CD4+ T-lymphocyte percentages of 15% or greater) should be immunized with the MMR vaccine.
• One attack of mumps (clinical or subclinical) usually confers lifelong immunity.
• Links of the MMR vaccine to autism by Andrew Wakefield in a 1998 Lancet publication have now been exposed as fraudulent, and multiple studies have documented no association between MMR vaccine and autism.

ETIOLOGY

• Epidemic parotitis is caused by mumps, an RNA virus in the Paramyxoviridae family.
• Other viral causes of parotitis include Epstein-Barr virus, cytomegaloviruses, influenza, parainfluenza, and enteroviruses.
• Parotid enlargement can be an initial sign in HIV-infected children.
• Bacterial cases are usually secondary to Staphylococcus aureus (suppurative parotitis).
• Streptococci, gram-negative bacilli, and anaerobic infections are also possible.
• Rare childhood cases may be secondary to an obstructing calculus, foreign body (sesame seed), tumors, sarcoid, Sjögren syndrome, or various drugs (antihistamines, phenothiazines, iodine-containing drugs/contrast media).

PATHOPHYSIOLOGY

• The virus is spread by contact with respiratory secretions.
• The mumps virus enters via the respiratory tract, and a viremia ultimately ensues.
• The virus spreads to many organs, including the salivary glands, gonads, pancreas, and meninges.
• Period of communicability: 7 days before to 9 days after onset of parotid swelling
• Most communicable period: 2 to 3 days before to 5 days after onset of parotid swelling
• Incubation period: 12 to 25 days after exposure (16 to 18 days most common)
• Humans are the only known host for mumps.

ASSOCIATED-CONDITIONS

• Salivary adenitis
  • Most common manifestation of mumps
  • 1/3 of cases occur subclinically.
• Epididymoorchitis
  • Up to 35% of adolescent mumps cases are complicated by orchitis.
  • Orchitis develops within 4 to 10 days of the onset of the parotid swelling.
  • Sterility is uncommon.
• Aseptic meningitis
• Pancreatitis
  • Mild inflammation is common.
  • Serious involvement is rare.