Overview
Infectious viral disease that can cause permanent paralysis. Globally on the verge of eradication — wild poliovirus type 1 remains endemic in Pakistan and Afghanistan.
Symptoms
Symptoms | Frequency | Severity | Onset |
|---|---|---|---|
| Fever | 85% | Mild | Early |
| Headache | 75% | Mild | Early |
| Malaise | 80% | Mild | Early |
| Irritability | 30% | Mild | Early |
| Loss of appetite | 45% | Mild | Early |
| Nausea | 40% | Mild | Early |
| Sore throat | 50% | Mild | Early |
| Vomiting | 35% | Mild | Early |
| Abdominal pain | 25% | Mild | Early |
| Diarrhea | 15% | Mild | Early |
| Paralysis | 1% | Critical | Peak |
| Back pain | 20% | Moderate | Peak |
| Dysphagia | 3% | Severe | Peak |
| Myalgia | 25% | Moderate | Peak |
| Neck stiffness | 15% | Moderate | Peak |
| Shortness of breath | 2% | Critical | Peak |
| Photophobia | 10% | Mild | Peak |
| Constipation | 20% | Mild | Peak |
| Tremor | 5% | Mild | Peak |
| Fatigue | 80% | Mild | Any phase |
Transmission
Overview
Highly infectious viral disease that can cause permanent paralysis.
Overview
Poliomyelitis is caused by poliovirus (types 1, 2, 3), an enterovirus transmitted primarily via the fecal-oral route. Most infections are asymptomatic or cause mild illness; <1% progress to paralytic disease. The Global Polio Eradication Initiative has reduced wild poliovirus cases by >99.9% since 1988.
Emergency Signs
Seek emergency medical care immediately if:
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Sudden weakness or paralysis of any limb — especially if asymmetric
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Difficulty breathing or swallowing
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Inability to raise the head against gravity
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Sudden severe back or neck pain with muscle weakness
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These symptoms in an unvaccinated child require urgent AFP reporting
Detailed Symptoms
Most common signs and symptoms
Asymptomatic infection: ~72% of cases
Abortive polio (minor illness, 3–5 days): Fever, sore throat, nausea, abdominal pain — resolves without sequelae.
Non-paralytic aseptic meningitis: Meningismus, muscle pain, stiffness — no paralysis.
Paralytic poliomyelitis (<1%): After an asymptomatic period following minor illness (biphasic fever), sudden onset of asymmetric flaccid paralysis, maximal within 2–5 days. Spinal type: limb weakness (legs > arms). Bulbar type: respiratory muscle and cranial nerve involvement — risk of respiratory failure. Post-polio syndrome can develop 15–40 years after recovery.
Knowing the symptoms is the first step to a quick response.
Course of Disease
Typical disease course (paralytic polio):
- Incubation period: 7–21 days (range 3–35 days).
- Minor illness (1–3 days): Fever, sore throat, malaise, headache, nausea, vomiting. Resolves in ~24% of infections (abortive polio).
- CNS phase / major illness (1–3 days): Recurrence of fever, headache, neck stiffness, meningeal signs. Muscle pain and spasms.
- Paralytic phase (hours to days): Asymmetric flaccid paralysis, typically legs > arms. Maximal paralysis usually develops within 3–4 days. Proximal > distal. No sensory loss (pure motor).
- Recovery (weeks to months): Maximum recovery within 6 months. Strength may continue to improve slowly for up to 2 years.
Spinal vs. bulbar: Spinal polio (limb paralysis) is most common. Bulbar polio involves cranial nerves and respiratory center — medical emergency.
Diagnosis
How this disease is identified
Suspect polio in any child <15 years with acute flaccid paralysis (AFP) or any age person with AFP in endemic/outbreak setting. Confirmation:
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Stool culture: poliovirus isolation (gold standard) — two specimens 24 hours apart, within 14 days of paralysis onset
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CSF analysis: lymphocytic pleocytosis, normal glucose, elevated protein
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Serology: not routinely used
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EMG: lower motor neuron pattern All AFP cases must be reported to national health authorities (polio-free zones) and WHO.
Treatment
Available treatment methods
No specific antiviral treatment is available for poliomyelitis. Management is supportive:
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Acute phase: analgesics, complete bed rest; hot packs for muscle spasm relief
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Respiratory support: mechanical ventilation for bulbar or respiratory involvement
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Physiotherapy: early passive range-of-motion exercises during acute phase; intensive rehabilitation during recovery phase
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Long-term rehabilitation: orthotics, surgical correction of deformities, assistive devices
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Post-polio syndrome: energy conservation, pain management, non-fatiguing exercise programs
Most cases are effectively treated with early diagnosis.
Prevention Details
How to protect yourself
Two highly effective vaccines are available:
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Inactivated Polio Vaccine (IPV): injectable
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no risk of vaccine-derived polio
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used in polio-free countries
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Oral Polio Vaccine (OPV): live-attenuated
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provides intestinal immunity
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rare risk of vaccine-derived poliovirus (VDPV) — being phased out WHO recommended schedule: IPV at 2, 4, 6–18 months, and 4–6 years. Booster for travelers to endemic/outbreak areas. Travelers to Pakistan, Afghanistan, or areas with circulating vaccine-derived poliovirus should receive a booster IPV dose within 4 weeks to 12 months before departure (required by GPEI exit requirements for residents/long-term visitors of endemic countries).
Preparation is the best protection.
Travel Advice
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Check polio vaccination status before all international travel.
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Travelers to Pakistan, Afghanistan, or cVDPV-affected areas: require proof of IPV vaccination (within 4 weeks to 12 months before departure from endemic country). Some countries require documentation on the International Certificate of Vaccination.
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Travelers from endemic countries may be required to show proof of vaccination at borders.
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Practice strict hand hygiene and food/water safety in areas with inadequate sanitation.
How common is it?
Statistics and geographic data
Since the Global Polio Eradication Initiative (1988), wild poliovirus cases fell from ~350,000/year to 6 (WPV1) reported in 2021. Wild poliovirus type 2 eradicated in 1999; type 3 in 2019. WPV1 remains endemic in Pakistan and Afghanistan. Circulating vaccine-derived poliovirus (cVDPV) outbreaks occur in areas with low OPV coverage, including parts of Africa, Middle East, and Asia. Over 200 countries have maintained polio-free status.
Risk Factors
Who is most at risk
Host factors increasing risk of paralytic disease:
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Age: Risk of paralysis increases with age at infection. Adults develop paralytic polio more frequently and with greater severity than children.
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Immunodeficiency: Primary immunodeficiency (especially B-cell defects such as agammaglobulinemia) dramatically increases risk of paralytic disease and chronic infection. These individuals can excrete vaccine-derived poliovirus for years (immunodeficiency-associated VDPV, iVDPV).
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Pregnancy: Pregnant women have a higher incidence of paralytic polio and higher case-fatality rates.
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Tonsillectomy: Prior tonsillectomy increases risk of bulbar polio.
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Intramuscular injections: Injections in the weeks before or during infection increase risk of paralysis in the injected limb ("provocation polio").
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Strenuous physical exercise: Physical exertion during the incubation period or early illness is associated with increased severity of paralysis.
Environmental and geographic risk factors:
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Lack of vaccination: Unvaccinated or under-vaccinated individuals in any country are at risk. Immunity gaps from missed routine immunization are the primary driver of cVDPV outbreaks.
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Poor sanitation: Fecal contamination of water supplies facilitates transmission.
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Conflict and displacement: Disruption of immunization programs in conflict zones (Afghanistan, Pakistan, parts of Africa) sustains transmission.
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Overcrowding: Close living conditions in camps or urban slums increase exposure risk.
Travel-related risk factors:
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Travel to endemic countries (Afghanistan, Pakistan) or countries with active cVDPV outbreaks
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Extended stays in rural areas with poor sanitation infrastructure
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Visiting friends and relatives (VFR) travelers may underestimate risk and delay vaccination
Complications Details
Potential complications
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Permanent flaccid paralysis: asymmetric limb weakness, most commonly legs; occurs in <1% of infections but leaves lifelong disability
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Respiratory failure: bulbar polio or high cervical spinal cord involvement; historically required iron lung
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Post-polio syndrome (PPS): gradual onset of new muscle weakness, fatigue, pain 15–40 years after initial infection, affecting ~25–40% of paralytic polio survivors
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Secondary musculoskeletal complications: scoliosis, joint deformities due to muscle imbalance
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Psychological impact: chronic disability, depression, social isolation
Recovery & Outlook
Expected outcomes and recovery
Asymptomatic infection: 72% of cases. No sequelae.
Abortive polio (minor illness): 24%. Complete recovery.
Non-paralytic aseptic meningitis: 1–5%. Full recovery within 2–10 days.
Paralytic polio: 0.5–1% of infections.
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CFR: 2–5% in children, 15–30% in adults (respiratory muscle involvement).
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Bulbar polio (brainstem involvement): CFR 25–75%.
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Partial or complete recovery of paralysis in 60% over 6–12 months. Residual paralysis is permanent.
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Post-polio syndrome: 25–40% of paralytic polio survivors develop new weakness, fatigue, and muscle atrophy 15–40 years later.
