I. Disease description VPD Surveillance Manual, 3 rd Edition,.pdf

VPD Surveillance Manual, 3 rd Edition, 2002 Chapter 10, Poliomyelitis: 10 - 1 Chapter 10: Poliomyelitis Joanne Cono, MD, ScM; Lorraine N. Alexander, RN, MPH I. Disease description Poliomyelitis is a highly contagious disease caused by three serotypes of poliovirus. Infection with poliovirus results in a spectrum of clinical manifestations from inapparent infection to non-specific febrile illness, aseptic meningitis, paralytic disease, and death. Two phases of acute poliomyelitis can be distinguished: a non-specific febrile illness (minor illness) followed, in a small proportion of patients, by aseptic meningitis and/or paralytic disease (major illness). The ratio of cases of inapparent infection to paralytic disease ranges from 100:1 to 1000:1. Following poliovirus exposure, viral replication occurs in the oropharynx and the intestinal tract. Viremia follows, which may result in infection of central nervous system cells. A specific receptor is needed for the virus to enter cells. Replication of poliovirus in motor neurons of the anterior horn and brain stem results in cell destruction and causes the typical clinical manifestations of poliomyelitis. Depending on the site of paralysis, poliomyelitis can be classified as spinal, bulbar, or spino-bulbar disease. Progression to maximum paralysis is rapid (2–4 days), usually associated with fever and muscle pain, and rarely continues after the temperature has returned to normal. Spinal paralysis is typically asymmetric, more severe proximally than distally, and deep tendon reflexes are absent or diminished. Bulbar paralysis may compromise respiration and swallowing. Between 2%–10% of cases of paralytic poliomyelitis are fatal. Infection with poliovirus results in lifelong, type-specific immunity. Following the acute episode, many patients recover muscle functions at least partially, and prognosis for recovery can usually be established within 6 months after ons