Poliomyelitis
Polioviruse,
that targeting motor neurons
Poliomyelitis
is caused by three serotypes of poliovirus, a neurotropic RNA virus of the family
Picornaviridae, genus Enterovirus.
Poliovirus type
1 has the highest ratio of paralytic infection to subclinical infection and is
the most frequent cause of epidemics of paralytic disease. Poliovirus types 2
and 3 are less neurovirulent. Type 2 wild poliovirus was the first serotype to
be eradicated in the Americas; as of 1999, the only remaining foci of type 2
wild poliovirus transmission were detected in northern India . Type 3 wild
poliovirus caused a major outbreak of paralytic disease in Angola in 1999 .
Poliomyelitis
is transmitted by person-to-person spread through facial-oral and oral-oral
routes, or occasionally by a common vehicle (e.g., water, milk). The incubation
period is typically 7-14 days (range, 3-35 days). When nonimmune persons are
exposed to wild poliovirus, inapparent infection is the most frequent outcome.