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
Tip
Over 72% of infections with poliovirus are asymptomatic. Clinical infection (mostly flu-like symptoms) is observed in less than 24% of cases and less than 1% of infected individuals develop paralysis.
- 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