Mumps virus

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  • Presents with a prodrome followed by parotitis


  • Enveloped single-stranded RNA virus in the genus Rubulavirus and family Paramyxovirus
  • Only one serotype but 13 genotypes (A to M)
  • Genome encodes eight proteins: hemagglutinin-neuraminidase (HN), fusion (F), nucleocapsid (NP), phosphoprotein (P), matrix (M), hydrophobic (SH) and L protein
    • P contains V and I proteins
  • Irregular spherical shape with nucleocapsid enclosed by a three-layered envelope
    • Surface studded with glycoproteins: HN and F, which are the most important for immunity
    • Middle layer is lipid bilayer from the host cell
    • Inner layer in membrane protein


  • Worldwide distribution
  • Epidemics every 2 to 5 years in unimmunized settings, with a peak between January and May
  • Spread primarily by schoolchildren
  • Outbreaks have happened amongst immunized people, suggesting that a third dose of MMR may be needed to confer ongoing immunity
  • Before vaccination, it was the leading cause of viral encephalitis and a common cause of viral meningitis


  • Acquired through virus (contact, droplet, fomites) entering nose or mouth, with tropism for endo/exocrine glands
    • Salivary, pancreatis, testicular
  • Less infectious that measles or varicella
  • Peak contagion is just before parotitis
  • Immune response begins with antibodies against NP protein (S antigen), and may be detectable at presentation, but decline quickly over months
  • Antibodies against HN protein (V antigen) follow, peaking at 2 to 4 weeks and persist for years
    • IgM antibodies fall within 2 to 6 months
  • Neutralizing antibodies to HN and F are detectable during convalescence

Clinical Manifestations

  • Incubation period of 16 to 18 days (range 2 to 4 weeks)
  • One-day prodrome of low-grade fever, anorexia, malaise, and headache
  • Earache and parotitis soon follow
    • Parotitis progresses over 2 to 3 days, with severe pain
    • The other parotid usually follows, but it can be unilateral
    • Stensen's duct is edematous and erythematous
    • Pain exacerbated by citrus
    • Can involve other salivary glands in 10%
  • Temperature can be as high as 40º C
  • Pain, fever, tenderness resolve, with parotid returning to normal within 1 week
  • Can lead to sialectasia resulting in recurrent or chronic sialadenitis

Mumps epididymo-orchitis

  • The most common extrasalivary gland manifestation, occuring in 20-30% of postpubertal men (bilateral in 15%)
  • Occurs in first 1-2 weeks after parotitis
  • Fevers up to 41º C, chills, headache, vomiting, and testicular pain
  • Swollen warm testicles with scrotal erythema
  • Fever resolves within 5 days, followed by slower resolution of the orchitis
    • Tenderness can sometimes last longer than 2 weeks
  • Longterm testicular atrophy in 50%
    • If unilateral, no concerns
    • If bilateral, sterility is rare, and impotence is not a sequela

Mumps oopheritis

  • In 5% of cases in postpubertal women
  • May cause impaired fertility

Mumps meningitis

  • Fever, headache, vomiting, and nuchal rigidity, with an aseptic CSF (lymphocyte-predominant more often than neutrophil-predominant)
    • Amylase may be elevated
  • Onset usually after parotitis, but can be 1 week before or up to 2 weeks after
  • Can also occur without parotitis
  • Lasts 3 to 10 days, with complete recovery

Mumps encephalitis

  • Non-focal encephalitis, high fever, altered LOC, seizures, paresis, aphasia, and involuntary movements, with an aseptic CSF
    • Fever can be up to 41º C
  • Can occur concurrent with or up to 10 days after onset of parotitis
  • Early-onset is from virus; late-onset is a postinfectious autoimmune demyelinating disease; but there is likely a continuum between these two extremes
  • Gradually resolves over 1 to 2 weeks
  • Can cause sequelae, including psychomotor retardation, seizures, and death

Other complications

  • Cerebellar ataxia, facial palsy, transverse myelitis, Guillain-Barré syndrome, and poliomyelitis-lik syndrome
  • Migratory polyarthritis, usually starting 10-14 days after parotitis and lasting up to 5 weeks
  • Pancreatitis
  • ECG changes with ST depression and T-wave changes, 1st degree heart block
    • Myocarditis is rare


  • Pregnant women who are infected have increased risk of spontaneous abortion in the first trimester, as well as low birth weight
  • Not clearly related to any significant birth defects

Differential Diagnosis


  • Traditionally a clinical diagnosis
  • CBC and diff are normal or mild leukopenia; amylase may be up from parotitis, or lipase from pancreatitis
  • Can be diagnosed with serology or PCR
  • ELISA for IgM, or a fourfold rise from acute to convalescent ELISA or HAI serologies, are diagnostic
    • HAI may be affected by parainfluenza
  • PCR or culture detectable in saliva, though relatively low level after 5 days; also found in CSF
    • Can be detected in urine up to 2 weeks after onset


  • Symptomatic
  • Immune globulin not helpful
  • Post-exposure immunization may not be helpful, though in an outbreak situation, may consider giving an MMR booster
  • Isolation for 5 days after onset of parotitis to reduce spread
  • Reportable disease, public health may do outbreak investigation and consider booster MMR in high-risk populations


  • Live attenuated vaccine in the MMR is given at 12-15 months and again at 4-6 years
  • Vaccine 65-70% effective, so need high vaccination rate to achieve herd immunity
  • Titres positive for at least 10 years, but immunity wanes
  • Contraindicated in pregnant women