Poliomyelitis
Poliomyelitis is caused by poliovirus, a fecal-orally transmitted picornavirus that destroys anterior horn motor neurons after hematogenous spread from the gut, producing asymmetric lower motor neuron flaccid paralysis in under 1% of infected people. Diagnosis rests on the clinical picture supported by cerebrospinal fluid lymphocytic pleocytosis and isolation of the virus from stool or throat secretions, treatment is supportive with ventilatory support for respiratory muscle involvement, and prevention is universal inactivated poliovirus vaccination in childhood.
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What this article covers
- Overview
Poliomyelitis is caused by poliovirus, a picornavirus (enterovirus) transmitted by the fecal-oral route, that replicates in oropharyngeal and intestinal lymphoid tissue before spreading hematogenously to the central nervous system.
- Epidemiology
Wild-type poliovirus has been eliminated from the Western Hemisphere and from most of the world, but continues to circulate as endemic infection in parts of Asia and Africa, with Afghanistan and Pakistan the last remaining endemic countries.
- Risk factors
Lack of, or incomplete, poliovirus vaccination, the dominant modifiable risk factor, since susceptibility is essentially eliminated by a completed vaccine series.
- Pathophysiology
Poliovirus is ingested and initially infects and replicates in the lymphoid tissue of the oropharynx and small intestine, the site of primary viral multiplication before any systemic spread occurs.
- Clinical features
Most infections are asymptomatic or produce only a nonspecific flu-like minor illness (fever, sore throat, malaise, headache, gastrointestinal upset) that resolves without any neurologic involvement.
- Differential diagnosis
Guillain-Barre syndrome: ascending, typically symmetric flaccid weakness with sensory symptoms and albuminocytologic dissociation on cerebrospinal fluid (CSF) analysis (elevated protein with a normal…
- Diagnosis
Poliomyelitis is diagnosed clinically from the characteristic acute, asymmetric lower motor neuron flaccid paralysis following a febrile meningitic prodrome, confirmed by isolation of poliovirus from…
- Management
First, assess respiratory and bulbar function immediately in any patient with suspected paralytic poliomyelitis, because respiratory muscle involvement can progress rapidly and is the dominant cause of mortality.
- Complications
Respiratory failure from involvement of the diaphragm and intercostal muscles, the most immediately life-threatening acute complication, requiring mechanical ventilation.
- Prognosis
Case fatality in paralytic poliomyelitis is driven primarily by respiratory and bulbar muscle involvement; with modern ventilatory support, most patients with respiratory failure survive the acute illness.
- Prevention
Give the inactivated poliovirus vaccine (IPV) as the routine childhood immunization, administered as a 4-dose series at 2 months, 4 months, 6 to 18 months, and 4 to 6 years of age in the United…
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- West Nile virus infection
West Nile virus (WNV) is a mosquito-borne flavivirus and the most common cause of epidemic viral encephalitis in the United States, transmitted by Culex mosquitoes between June and October. Most infections are asymptomatic, but neuroinvasive disease can present as meningitis, encephalitis with basal ganglia involvement (tremor, parkinsonism, myoclonus), or acute flaccid paralysis resembling poliomyelitis; diagnosis is by WNV IgM in serum or CSF, and treatment is supportive because no specific antiviral or vaccine exists.
- Vaccines
Vaccines are live attenuated, inactivated, subunit, conjugate, or toxoid preparations that induce antigen-specific active immunity to prevent infection or its complications before exposure occurs. Selection follows the age- and risk-based Advisory Committee on Immunization Practices schedule, with routine adult boosting such as Tdap every 10 years, and inactivated regimens substituted whenever a live vaccine is contraindicated by pregnancy or immunosuppression.