Epidemiology

• Poliovirus is still endemic in Afghanistan and Pakistan.

Etiology

• Fecal-oral: absorption of poliovirus in the intestinal tract
• Incubation time: 7-14 days

Pathophysiology

The virus replicates in the gastrointestinal tract (oropharynx and small intestine) following oral ingestion → enters the bloodstream → potential invasion of the gray matter of the spinal cord (particularly the lower motor neurons of the anterior horn) → myelitis

Clinical features

• Fever, malaise, headache, nausea
• Severe back, neck, and muscle pain
• Asymmetric acute flaccid paralysis worsens over hours to days
  • Most commonly affects the leg muscles
  • Paralysis is usually more severe in proximal muscles than in distal muscles.
  • Ascending paralysis with diaphragmatic involvement → respiratory failure

Diagnostics

• Confirmatory test: PCR of CSF, stool, or oropharyngeal samples to test for poliovirus RNA
• CSF will show:
  • High protein levels
  • Pleocytosis with either neutrophils (early infection) or lymphocytes (late infection)

Differential Diagnosis

• Guillain-Barré syndrome: Paralysis is typically symmetrical in Guillain-Barré syndrome. In addition, it would not manifest with CSF pleocytosis.
• Acute intermittent porphyria: may also present with muscle weakness and bulbar paralysis
• Spinal muscular atrophy: Paralysis is typically symmetrical.

Treatment

• Pain relief
• Airway management and mechanical ventilation if needed

Complications

• Post-polio syndrome (PPS)
  • Most frequent complication observed following poliovirus infection (up to 40% of survivors)
  • Occurs decades after infection
  • Manifests with progressive muscle weakness and pain