Poliovirus types 1, 2 and 3 (three closely related enteroviruses).
Polio viruses are spread predominantly by the faecal–oral route. In settings with high standards of hygiene, the oral–oral route of transmission may also be common.
Nature of the disease
Poliomyelitis, also known as polio or infantile paralysis, is a disease of the central nervous system. Following primary asymptomatic infection of the alimentary tract, fewer than 1% develop paralytic disease. In developing countries, 65–75% of cases occur in children under 3 years of age and 95% in children under 5 years of age. The resulting paralysis is permanent, although some recovery of function is possible. There is no cure.
Significant progress has been made towards global eradication of polio.As of March 2014, wild poliovirus remains endemic in three countries – Afghanistan, Nigeria and Pakistan. In 2013, outbreaks following importation of wild poliovirus from endemic countries occurred in the Horn of Africa (Somalia, Ethiopia, Kenya), Syria and Cameroun. Evidence of wild poliovirus transmission was also documented in Israel Polio cases due to circulating vaccine-derived poliovirus (cVDPV) were reported in 2013 from Nigeria, Niger, Chad, Cameroun, Pakistan, Afghanistan, Somalia and Yemen.
Risk for travellers
Until the disease has been certified as eradicated globally, the risks of acquiring polio (for travellers to infected areas) and of reinfection of polio-free areas (by travellers from infected areas) remain. All travellers to and from countries and areas infected by wild or circulating vaccine-derived poliovirus should be adequately vaccinated. Updates on countries which are considered to be polio infected currently can be found at www.polioeradication.org/casecount.asp.