What percentage of people infected with poliomyelitis (polio) die or have permanent injury?

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Last updated: January 24, 2026 • View editorial policy

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Mortality and Permanent Injury Rates in Polio Infection

Among all people infected with poliovirus, approximately 0.1-1% develop paralytic disease, and of those who develop paralysis, 2-10% die during the acute phase, while the majority of survivors retain some degree of permanent paralysis. 1

Acute Phase Outcomes

Infection-to-Paralysis Ratio

  • Most poliovirus infections (99-99.9%) are asymptomatic or cause only mild illness, with paralytic polio occurring in only 0.1-1% of all infections, representing a ratio of inapparent infection to paralytic disease of 100:1 to 1,000:1. 1
  • When paralysis does occur, it progresses rapidly to maximum severity within 2-4 days. 1

Acute Mortality

  • Paralytic polio is fatal in 2-10% of cases during the acute phase, with the highest mortality occurring in patients requiring respiratory support. 1
  • Research confirms that patients treated for respiratory failure during epidemics had significantly elevated mortality (standardized mortality ratio = 2.71). 2

Recovery and Permanent Disability

  • Many patients recover at least some muscle function after the acute episode, though the extent varies considerably. 1
  • The prognosis for recovery can usually be established within 6 months after onset of paralytic manifestations. 1
  • Among those who survive paralytic polio, most retain some degree of permanent weakness or paralysis, with severity ranging from minimal residual weakness to severe disability. 1

Long-Term Consequences

Post-Polio Syndrome

  • After 30-40 years, 25-40% of persons who contracted paralytic polio during childhood develop post-polio syndrome, characterized by new muscle weakness, muscle pain, and exacerbation of existing weakness. 1, 3
  • Risk factors include longer time since acute infection, more severe permanent residual impairment after recovery, and female gender. 1
  • The rate of muscle strength decline in post-polio syndrome averages 1% per year, with irregular progression and plateau periods. 4

Long-Term Mortality

  • Survivors of paralytic poliomyelitis have moderately increased long-term mortality (Hazard Ratio 1.31) compared to the general population. 5
  • Excess mortality is particularly pronounced among patients with severe paralysis of the extremities (standardized mortality ratio = 1.69) and those who required respiratory support (standardized mortality ratio = 2.71). 2
  • Long-term mortality does not appear to increase significantly until 20 years after discharge, except for those with respiratory failure. 2

Summary of Overall Impact

To directly answer the question: Of all people infected with poliovirus, less than 1% develop paralysis, 0.002-0.1% die acutely (2-10% of the 0.1-1% who develop paralysis), and approximately 0.1-1% have permanent injury from paralytic disease. 1 Additionally, 25-40% of paralytic polio survivors will develop late deterioration through post-polio syndrome decades later. 1, 3

References

1
Guideline

Polio Disease Characteristics and Progression

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

2
Research

Long-term mortality after poliomyelitis.

Epidemiology (Cambridge, Mass.), 2003

3
Guideline

Post-Polio Syndrome Surveillance

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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