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Mumps

BASICS

Description

  • Acute, self-limited paramyxovirus infection, usually presenting with parotitis
  • Asymptomatic: up to 30% of nonimmune, 60% of vaccinated
  • Parotitis: 95% of symptomatic
  • Transmission: respiratory droplets, saliva contact
  • Incubation: 12–25 days, then 2–3 days of symptoms

EPIDEMIOLOGY

  • 85% of cases: <15 years old; males = females
  • R0 = 10 (highly contagious)
  • Peak: unvaccinated children 5–15 y; rare <2 y
  • Maximal contagion: 24h before to 72h after parotitis onset
  • Case rate dropped from 100/100,000 to 1.1/100,000 post-vaccination

ETIOLOGY & PATHOPHYSIOLOGY

  • RNA virus: Rubulavirus (Paramyxovirus)
  • Replicates in parotid, pancreas, testes, rarely kidneys
  • Edema/inflammation in glands; testicular edema can cause necrosis/loss of function

RISK FACTORS

  • Global travel (areas with low vaccination)
  • Crowded environments (dorms, barracks, jails)
  • Waning immunity after single-dose or years post-vaccination

PREVENTION

  • Vaccination (2 doses MMR/MMR-V): 12–15 mo, 4–6 y (can start at 6 mo for travelers)
  • Efficacy: 68–95%
  • Adherence: 95% (1st dose), >80% (2nd dose)
  • No link between MMR and autism
  • No benefit from Ig or postexposure vaccine
  • Isolation: 5 days after parotitis (droplet), 26 days (contacts in outbreaks)
  • 3rd MMR dose may be used in epidemics

Pregnancy

  • Live vaccines contraindicated; OK to vaccinate children if a household member is pregnant
  • No risk to breastfed infants

DIAGNOSIS

History

  • Parotid swelling (peaks 1–3 days, lasts 3 days, up to 7)
  • Fever, myalgias, malaise, anorexia (rare prodrome)
  • Sour foods: pain in parotid
  • High fever = complications more likely

Physical Exam

  • Painful parotid swelling (95% bilateral), obscures mandible, elevates earlobe
  • Redness at Stensen’s duct (no pus)
  • Meningeal signs (15%), rash, rare sternal swelling

Differential Diagnosis

  • Other viral/bacterial parotitis (EBV, influenza, CMV, HIV, etc.)
  • Suppurative parotitis (pus)
  • Salivary calculi, allergic parotitis, lymphadenitis, Mikulicz, Sjögren, drug-induced
  • Orchitis: rule out torsion, bacterial, chlamydial

Diagnostic Tests

  • Buccal/oral swab PCR (best within 1–3 days of parotitis)
  • Serum IgM, IgG (less sensitive in vaccinated)
  • Urine PCR (less sensitive, ≥4 days post-onset)
  • Testicular US: orchitis vs torsion
  • CSF: for meningitis signs
  • Reportable: notify health dept

TREATMENT

  • Supportive care only; no antivirals
  • Analgesics/NSAIDs/acetaminophen for pain and fever
  • Avoid aspirin in children (Reye syndrome)
  • Avoid steroids in orchitis (risk of testicular atrophy)
  • Interferon-α2b for severe orchitis (second line)
  • IVIG: postinfectious encephalitis, GBS, ITP (autoimmune sequelae)
  • Hospitalization: high fever, CNS symptoms, pancreatitis

GENERAL MEASURES

  • Isolation/mask in clinical settings
  • Orchitis: ice, scrotal support (bed rest, supportive clothing)
  • Liquid diet if unable to chew

ONGOING CARE

  • School exclusion: 5 days after parotid pain starts
  • Contact exclusion: 26 days if unvaccinated
  • Hydration monitoring

PROGNOSIS

  • Complete recovery typical; lifelong immunity
  • Complications:
  • Orchitis: 20–30% postpubertal males (rare sterility)
  • Meningitis, encephalitis, ataxia, oophoritis, mastitis, pancreatitis, nephritis, deafness
  • Hearing loss: 4% transient, 1/1,000 permanent in children
  • Death rare (meningoencephalitis, myocarditis)
  • Pregnancy: may ↑ 1st trimester loss risk; perinatal mumps usually benign

ICD-10

  • B26.3: Mumps pancreatitis
  • B26.2: Mumps encephalitis
  • B26.81: Mumps hepatitis

Clinical Pearls

  • Diagnosis: parotid swelling ≥2 days, no other cause
  • Confirm: PCR, culture, serology
  • Work with health authorities for specimen/reporting
  • Ultrasound: orchitis vs torsion
  • Vaccination does not fully exclude mumps if distant
  • Immunity wanes over time; outbreaks possible despite vaccination