No deaths due to wild-type poliovirus have been reported in the US since 1979. Most patients infected with poliovirus develop inapparent infections and are frequently asymptomatic. 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 usually involve groups of muscles that were initially affected.
Patients usually develop meningitis with lymphocytic pleocytosis.
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 generally is observed several weeks after the beginning of symptoms. Recovery may be complete, partial, or absent. These viruses are resistant to ether and chloroform but can be inactivated by formaldehyde. They multiply in the gastrointestinal tract but are particularly neurotropic.