Polio (poliomyelitis) is a contagious, acute viral disease caused by poliovirus, a highly infectious enterovirus belonging to the family Picornaviridae. The human is the only natural host for the virus. There are three poliovirus serotypes (type 1, 2 and 3), each of which can cause polio.
The virus is spread person-to-person, typically through faecal-oral route (eg contaminated water, contaminated hands). It enters the body through the mouth, replicates in the intestines and is subsequently excreted in the faeces. During passage through the intestines, it can enter the blood stream to invade the central nervous system, where it spreads along nerve fibres.
Less than 1% of cases result in varying degrees of irreversible paralysis (usually in the legs), and possible death [1,2]. Most infected people have no or very mild flu-like symptoms. Thus infection with the poliovirus usually goes unrecognized.. However, post-polio syndrome may occur years after infection, with a slow development of muscle weakness. The death rate for paralytic polio is 2-5% among children and up to 15-30% for adults .