eMedicine Specialties > Pediatrics: General Medicine > Infectious Disease
Poliomyelitis
Updated: Aug 15, 2007
Introduction
Background
Poliomyelitis is an enteroviral infection that can manifest in 4 different forms: inapparent infection, abortive disease, nonparalytic poliomyelitis, and paralytic disease. Before the 19th century, poliomyelitis occurred sporadically. During the 19th and 20th centuries, epidemic poliomyelitis was more frequently observed, reaching its peak in the mid 1950s. The worldwide prevalence of this infection has decreased significantly since then because of aggressive immunization programs. Eradication of this disease during the present decade is a top priority for the World Health Organization (WHO).
Pathophysiology
Poliovirus is an RNA virus that is transmitted through the oral-fecal route or by ingestion of contaminated water. Three serotypes are able to cause human infection. The incubation period for poliovirus is 5-35 days. The viral particles initially replicate in the nasopharynx and gastrointestinal tract and then invade lymphoid tissues, with subsequent hematologic spread. After a period of viremia, the virus becomes neurotropic and produces destruction of the motor neurons in the anterior horn and brainstem. The destruction of motor neurons leads to the development of flaccid paralysis, which may be bulbar or spinal in distribution.
Frequency
United States
No cases of wild-type poliovirus infection have been reported in the United States since 1979. Until 1998, an average of 8-10 cases associated with the vaccine virus were reported every year. Since the institution of an all-inactivated poliovirus vaccine (IPV) policy in the routine immunization schedule, the number of vaccine-associated cases has significantly decreased. Four cases of vaccine-derived poliovirus were identified in 2005 among unvaccinated children in an Amish community in Minnesota.
International
The global incidence of poliovirus infection has decreased by more than 99% since 1988. Although no outbreaks had been reported in the western hemisphere since 1991, the Pan American Health Organization reported an outbreak in Haiti and the Dominican Republic in 2001. Since 2001, no additional outbreaks of disease caused by wild poliovirus have been reported in the Americas. Clusters of wild-type disease are still found in some areas in Africa and Southeast Asia. By 2004, the only 6 countries in which wild poliovirus transmission had not been interrupted were India, Egypt, Nigeria, Niger, Pakistan, and Afghanistan. Although significant progress has been made towards eradication of this infection in these countries, an increase in the number of cases was observed in 2006.
Mortality/Morbidity
Mortality is more frequently observed in cases of paralytic poliomyelitis and is associated with complications such as respiratory failure. No deaths due to wild-type poliovirus have been reported in the United States since 1979.
Although most cases of poliomyelitis (90-95%) are inapparent, 5-10% of patients who acquire this infection develop symptoms.
Sex
Males and females of pediatric age are affected with equal frequency.
Age
Poliovirus affects mainly children. However, individuals of any age (especially those who are immunocompromised) may also develop the disease.
Clinical
History
- Most patients infected with poliovirus develop inapparent infections and are frequently asymptomatic.
- In cases of abortive poliomyelitis (5-10%), a history of the following is found with normal neurologic examination findings:
- Anorexia
- Vomiting
- Abdominal pain
- Duration of illness usually less than 5 days
- When nonparalytic poliomyelitis develops, symptoms usually are those observed in abortive disease in addition to meningeal irritation.
- Paralytic poliomyelitis involves systemic manifestation, such as respiratory failure, in addition to symptoms observed in nonparalytic poliomyelitis.
- Patients who have recovered from poliomyelitis occasionally develop a postpoliomyelitis syndrome, in which recurrences of weakness or fatigue are observed and which usually involve groups of muscles that were initially affected. This postpolio syndrome may develop 20-40 years after infection with poliovirus.
Physical
The spectrum of disease varies from inapparent infection to paralytic disease.
- In mild cases, the following nonspecific signs and symptoms are observed and usually resolve within a few days:
- Fever
- Headache
- Nausea
- Vomiting
- Abdominal pain
- Oropharyngeal hyperemia
- Nonparalytic poliomyelitis is characterized by the symptoms described above in addition to the following:
- Nuchal rigidity
- More severe headache
- Back and lower extremity pain
- Meningitis with lymphocytic pleocytosis (usually)
- Paralytic poliomyelitis occurs in fewer than 5% of affected patients and is characterized by the following:
- Compromise of the motor neurons may be localized or widespread.
- More frequently, asymmetric loss of muscle function is observed with involvement of major muscle groups.
- Muscle atrophy is generally observed several weeks after the beginning of symptoms.
- Recovery may be complete, partial, or absent.
Causes
Polioviruses are enteroviruses within the Picornaviridae family. These viruses are resistant to ether and chloroform but can be inactivated by formaldehyde. They multiply in the gastrointestinal tract but are particularly neurotropic.
Documentation suggests that infections with polioviruses can be potentiated by factors such as exercise and tonsillectomy. Additionally, patients who are immunocompromised, such as those with human immunodeficiency virus (HIV) infection, B-cell disfunction, immunoglobulin A (IgA) deficiency, or severe combined immunodeficiency, are particularly at high risk of developing poliomyelitis when exposed to both wild-type polioviruses and vaccine-attenuated viruses present in the oral poliovirus vaccine.
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| Follow-up: Poliomyelitis |
| References |
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References
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Further Reading
Keywords
poliomyelitis, flaccid paralysis, nonparalytic poliomyelitis, paralytic poliomyelitis, wild-type poliovirus
