Virus

Polio

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Polio, Epidemic Acute Polio, Poliomyelitis, Human Poliovirus, Polio Encephalomyelitis, Polioencephalitis, Abortive Poliomyelitis, Acute Paralytic Poliomyelitis, Bulbar Poliomyelitis, Postpoliomyelitis Syndrome, Postpoliomyelitis Muscle Atrophy, Post-Polio Syndrome, Post Polio Syndrome

  • See Also
  1. Transverse Myelitis
  2. Acute Flaccid Paralysis
  3. Acute Flaccid Myelitis
  4. Spinal Cord Syndrome
  5. Cauda Equina Syndrome
  6. Acute Motor Weakness Causes
  7. Peripheral Neuropathy
  8. Symmetric Peripheral Neuropathy (Polyneuropathy)
  9. Asymmetric Peripheral Neuropathy (Mononeuropathy)
  10. Guillain Barre Syndrome
  11. Botulism
  12. Floppy Infant
  • 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
  • Pathophysiology
  1. Polio is an Enterovirus in the Picornaviridae Family
  2. Picornaviridae
    1. Picornaviridae are a family of non-enveloped (naked) RNA Viruses with an icosahedral capsid
    2. Picornaviridae are Message Sense RNA Viruses (Positive Stranded, +ssRNA)
      1. Message sense RNA (+ssRNA) are identical to Messenger RNA (mRNA)
      2. Like mRNA, +ssRNA may be immediately translated by host ribosomes into Protein
  3. Enteroviruses
    1. Enteroviruses infect small intestinal epithelial cells (peyer's patches) and lymphoid cells (Tonsils)
    2. Enteroviruses may also infect other tissue, such as Motor Neurons, as with Polio
    3. Enterovirus transmission is via pharyngeal secretions and via fecal-oral route
  4. Transmission: Polio is only infectious to humans, with person to person spread
    1. Fecal-oral route
    2. Respiratory route
  5. Polio Replication
    1. Polio replicates in the Tonsils and the Peyer patches (Small Intestines)
    2. Polio spreads hematogenously, across the blood brain barrier
    3. Polio specifically infects the spinal cord at the anterior horn
      1. Destruction of presynaptic Motor Neurons (Upper Motor Neuron effects)
      2. Destruction of postsynaptic Motor Neurons (Lower Motor Neuron effects)
  • 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)
  • 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 to 1 week
  5. Paralytic Poliomyelitis (1%)
    1. Initial mild febrile illness resolves
    2. Fever recurs 5-10 days later accompanied by meningismus and asymmetric Flaccid Paralysis
  • 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. Age >15 years and 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 (no sensory deficits)
  • Differential Diagnosis
  1. See Acute Flaccid Paralysis
  2. See Acute Flaccid Myelitis
  3. See Transverse Myelitis
  4. See Peripheral Neuropathy
  5. See Guillain Barre Syndrome
  6. See Floppy Infant
  7. Heavy Metal Poisoning
  8. Botulism
  • 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
  • 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
  • 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
  • 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)
  • 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
  • Prevention
  1. See Polio Vaccine
  • Resources
  1. Polio (CDC)
    1. https://www.cdc.gov/polio/us/hcp.html
  2. Poliomyelitis (Stat Pearls)
    1. https://www.ncbi.nlm.nih.gov/books/NBK558944/
  • References
  1. (1991) Harrison Internal Medicine, 12th ed, p.713-4