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Poliomyelitis

Last updated: March 18, 2021

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Poliomyelitis, or polio, is a disease caused by poliovirus, a type of human Enterovirus. Poliovirus spreads via fecal-oral transmission. Although the majority of poliovirus infections are asymptomatic, some may invade the central nervous system, leading to motor neuron death and irreversible paralysis that can cause respiratory insufficiency and death. The main clinical manifestations of poliomyelitis are weakness, decreased muscle tone, and hyporeflexia. The diagnosis is established based on polymerase chain reaction (PCR) findings of poliovirus RNA in cerebrospinal fluid. Poliomyelitis has been eradicated in most parts of the world thanks to the success of global vaccination initiatives. The treatment of poliomyelitis is mainly supportive. Patients with brainstem or respiratory muscle involvement may require intubation and mechanical ventilation. The majority of patients do not regain their full strength after recovery. Some patients go on to develop post-polio syndrome, a poorly understood syndrome characterized by progressive disability and muscle weakness decades after the initial polio infection.

  • Due to widespread vaccination measures, poliomyelitis has been eradicated from the US and most other countries.
  • Poliovirus is still endemic in Afghanistan and Pakistan.

Epidemiological data refers to the US, unless otherwise specified.

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. The clinical forms of poliomyelitis are: [1][2]

Poliomyelitis without CNS involvement (abortive poliomyelitis)

Poliomyelitis with CNS involvement

Nonparalytic poliomyelitis: aseptic meningitic form

  • Begins several days following abortive poliomyelitis (often temporary, symptom-free interval)
  • Fever, neck stiffness, headache, vomiting, muscle pain
  • Neck muscle weakness (head drop sign: head falls back when placed in a supine position)
  • No paresis

Paralytic poliomyelitis

  • Post-polio syndrome (PPS) [3]
    • Most frequent complication observed following poliovirus infection (up to 40% of survivors)
    • Occurs decades after infection
    • Manifests with progressive muscle weakness and pain, even in areas that were not affected by the initial infection

The differential diagnoses listed here are not exhaustive.

  • The prognosis is dependent on the form of poliomyelitis.
  • In the abortive and nonparalytic forms, complete recovery without complications occurs within 2 weeks.
  • In the paralytic form, the most serious short-term risk is death due to diaphragmatic involvement. After recovery, most patients have residual deficits, including muscle weakness or contractures and muscle pain.
  • Post-polio syndrome may lead to muscle weakness and pain decades after polio infection.
  • Immunization
    • The inactivated poliovirus vaccine (IPV) is recommended for childhood immunization in the US and most high-income countries.
    • In the US, children receive 4 doses of IPV, at 2, 4, and 6–18 months; , followed by a booster dose at 4–6 years; . See “Immunization schedule.”
    • The live attenuated oral poliovirus vaccine (OPV) is used for childhood immunization in resource-limited countries because it is less costly. It has a slightly increased risk of vaccine-associated paralytic polio and is being gradually replaced in favor of the IPV worldwide.
  1. Global Health: Polio. https://www.cdc.gov/polio/about/index.htm. Updated: October 15, 2014. Accessed: March 2, 2017.
  2. Epidemiology and Prevention of Vaccine-Preventable Diseases.
  3. Post-Polio Syndrome. https://www.cdc.gov/polio/us/pps.html. Updated: August 2, 2016. Accessed: June 13, 2017.