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.
• However, mumps remains endemic in the United States, and outbreaks continue to occur.
  • Cases in the United States have ranged from several hundred to several thousand cases annually.
  • Since 2014, >1,000 cases per year are typically reported in the United States, with 3,780 cases reported in 2020.
• Outbreaks
  • Most outbreaks have been linked to being in close contact, crowded environments, 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.
  • Waning immunity to mumps vaccine contributes to the endemicity of mumps and outbreaks among those in close-contact settings.

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, enteroviruses, adenovirus, and human immunodeficiency virus (HIV).
• Parotid enlargement can be an initial sign of HIV infection in 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).

GENERAL PREVENTION

• Two combination mumps vaccine are used:
  • MMR: measles, mumps, rubella
  • MMRV: measles, mumps, rubella, varicella
• A single 0.5-mL subcutaneous (SC) injection of live mumps vaccine (MMR or MMRV) is recommended at 12 to 15 months.
• A second vaccination (MMR or MMRV) is recommended between 4 and 6 years of age.
• MMRV can be given at 12 to 15 months of age but has a slightly higher risk of febrile seizures than when MMR and varicella vaccines are given separately at that age.
• MMRV is generally preferred for the second dose of vaccine to minimize the number of injections.
• The efficacy of 2 doses of vaccines is estimated at approximately 80–90%.
• Primary vaccine failure and waning vaccine–induced immunity have been reported.
• Waning immunity contributes to mumps outbreaks, despite complete vaccination.
• 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.
• Vaccine should not be administered to children who are immunocompromised by disease or pharmacotherapy or to pregnant women.
• If a child has recently received immunoglobulin (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 ≥15%) 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.

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 (parotitis typically occurs 16 to 18 days after exposure)
• Humans are the only known host for mumps.

COMMONLY ASSOCIATED CONDITIONS

• Salivary adenitis
  • Most common manifestation of mumps
  • One third of cases occur subclinically.
• Epididymoorchitis
  • Up to 35% of adolescent mumps cases are complicated by orchitis in unvaccinated individuals. Frequency of this complication in previously mumps-vaccinated individuals is much lower.
  • 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.
  • Occurs less commonly in previously mumps-vaccinated individuals