Poliomyeletis

Poliomyeletis

The most recognizable feature of poliomyelitis is onset of acute flaccid paralysis (AFP)

AFP, when it occurs, is of gradual onset (2–4 days); typically asymmetric and usually involves lower rather than upper limbs. Bulbar (brainstem) paralysis leading to respiratory depressions accounts for the 2–10% mortality rate associated with paralytic poliomyelitis. After the acute illness, there is often a degree of recovery of muscle function; 80% of eventual recovery is attained within 6 months, although recovery of muscle function may continue for up to 2 years.

Symptoms

This symptom occurs in less than 1% of Poliovirus infections. More than 90% of those infected have asymptomatic infections or a mild, non- specific febrile illness that lasts a few days. An abrupt onset of meningitic and neuromuscular symptoms, such as neck stiffness and pain in the limbs follow in a few cases, associated with fatigue, headache, vomiting and constipation (or less commonly, diarrhoea).

After many years of stable neurological impairment, new neuromuscular symptoms (post-polio syndrome) may develop in 25–40% of patients.

Infectious Agents

The infectious agent is Poliovirus (of the Enterovirus genus group). Types 1, 2 and 3 can all cause paralysis. Type 1 is the type most often isolated from paralytic cases and associated with epidemics. Most vaccine-associated cases are classified as type 2 or 3.

Mode of transmission

Poliovirus is transmitted mainly via the faecal–oral route.

Prevention

Immunization is vital for the prevention of poliomyelitis.

  1. Polio reported cases. Geneva, World Health Organization (WHO), 2010 (http://www.who.int/ immunization_monitoring/en/globalsummary/timeseries/tsincidencepol.htm, accessed
  2. 9 August 2010).Reported third dose coverage estimates for trivalent oral polio vaccine (OPV), Geneva, WHO, 2010 (http://apps.who.int/immunization_monitoring/en/globalsummary/timeseries/ tscoveragepol3.htm, accessed 9 August 2010).