II. Epidemiology

  1. Most often in children <15 years old (esp. infants and young children)
  2. Summer and Fall (temperate climates) or year round (tropical climates)
  3. Incidence: Paralytic Polio (U.S.)
    1. 1950s: 15,000 cases per year
    2. 1960s: <100 cases per year
    3. 1970s: <10 cases per year
    4. 1979: No wild-type cases onset in U.S. since this time
    5. 1993: Last internationally imported case of polio in U.S.
  4. Incidence: Worldwide
    1. Polio is still a risk to travelers to developing countries
      1. Those travelers may reintroduce Polio on their return to the U.S.
    2. Polio cases still occur in developing countries throughout the world
      1. Afghanistan, Pakistan and Syria
      2. Africa (Nigeria, Somalia, DR Congo, Niger, Mozambique, Cameroon, Chad, Central Africa Republic, Kenya)
      3. Papua New Guinea

III. Risk Factors

  1. Developing world
    1. Infants and young children
    2. Poor hygienic living conditions
    3. Under-immunized populations
  2. Travelers
    1. Unimmunized or under-immunized with Polio Vaccine
    2. Travel to remaining Polio endemic regions of the world (see above)
    3. Contact with persons traveling to Polio endemic regions of the world (see above)

IV. Pathophysiology

  1. Enterovirus infection (Picornaviridae)
  2. Only infectious to humans, with person to person spread
    1. Fecal-oral route
    2. Respiratory route

V. Presentations

  1. Incubation
    1. Non-paralytic polio: 3-6 days
    2. Paralytic polio: 7-21 days (from exposure to paralysis)
  2. Subclinical or asymptomatic (72%)
    1. Mild presentations
  3. Abortive Poliomyelitis (24%)
    1. Non-specific febrile illness for 2-3 days
    2. No CNS symptoms
  4. Aseptic Meningitis
    1. Rapid and complete recovery within a few days
  5. Paralytic Poliomyelitis (1%)
    1. Initial febrile illness resolves, followed a few days later by asymmetric Flaccid Paralysis

VI. Findings: Paralytic Poliomyelitis

  1. Prodrome: Fever and minor, non-specific symptoms (resolves within 2-5 days)
    1. Fever
    2. Pharyngitis
    3. Fatigue
    4. Headache
    5. Nausea
    6. Epigastric Pain
  2. Paralysis (onset 5-10 days after prodrome)
    1. Fever recurrence
    2. Meningeal Irritation
    3. Asymmetric Flaccid Paralysis
      1. Starts with cramping Muscle pain, spasms and course Muscle Twitching
      2. Maximal paralysis occurs within days of onset
      3. Descending paralysis
        1. Starts proximally in affected limb, and progresses distally
    4. Distribution
      1. Age <5 years
        1. Paralysis of one leg
      2. Age 5-15 years
        1. Weakness of one arm or Paraplegia
      3. Adults
        1. Quadriplegia
        2. Respiratory Muscle dysfunction
        3. Bladder dysfunction
        4. Bulbar Paralysis (6-25% of cases)
  3. Other neurologic findings
    1. Deep Tendon Reflexes decreased or absent
    2. Sensation intact

VIII. Diagnosis: Probable Paralytic Polio Case

  1. Acute Flaccid Paralysis (one or more limbs) AND
  2. Decreased or absent Deep Tendon Reflexes (in affected limbs) AND
  3. No sensory loss AND
  4. No cognitive loss AND
  5. No other apparent cause

IX. Diagnosis

  1. Precautions
    1. Cerebrospinal fluid has poor Test Sensitivity for polio and does not exclude polio
  2. Poliovirus PCR, Viral Isolation, Intratypic Differentiation
    1. Obtain within 14 days of symptom onset (ideally)
    2. Sources: Obtain 2 of each source at least 24 hours apart
      1. Stool specimens
      2. Throat swabs

X. Management

  1. Supportive Care
  2. Isolate any patient suspected of polio to prevent transmission to others
  3. Immediately report any suspected case of polio to local health department
    1. Confirmed Polio cases require CDC report within 4 hours

XI. Complications: Acute

  1. Myocarditis
  2. Hypertension
  3. Pulmonary Edema
  4. Secondary Infections (e.g. Pneumonia, Urinary Tract Infection)
  5. Respiratory Failure (2-10% of paralytic polio cases)

XII. Complications: Chronic

  1. Post-Poliomyelitis Neuromuscular Atrophy (Post-Polio Syndrome)
    1. Onset 15-40 years after initial polio presentation in 25-40% of polio survivors
    2. Slow degeneration of axon terminals in surviving Motor Neurons, with late denervation of Muscle
    3. Progressive and irreversible Muscle Weakness, Fatigue and Joint Pain

XIII. Prevention

XIV. Resources

XV. References

  1. (1991) Harrison Internal Medicine, 12th ed, p.713-4

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