poliovirus

Poliovirus is a non-enveloped, icosahedral, positive-sense single-stranded RNA virus in the genus Enterovirus of the family Picornaviridae. It exists in three serotypes, PV1, PV2, and PV3, each capable of causing poliomyelitis in humans.

Transmission occurs primarily via the fecal-oral route through contaminated water or food. After ingestion, the virus replicates in the oropharynx and intestinal mucosa and is shed in feces for weeks, enabling transmission to others. It can invade the bloodstream and, in some cases, spread to the central nervous system.

Most infections are asymptomatic or present as a mild febrile illness. A minority involve the nervous system, leading to aseptic meningitis or acute flaccid paralysis when motor neurons in the spinal cord’s anterior horns or brainstem are damaged. Paralytic poliomyelitis may result in permanent disability or death due to respiratory failure.

Prevention relies on vaccination. The two main vaccines are inactivated poliovirus vaccine (IPV) and oral poliovirus vaccine (OPV). OPV uses live attenuated strains and can, in rare cases, revert to neurovirulence, causing vaccine-derived poliovirus outbreaks. Global eradication efforts have used OPV extensively, with a switch in 2016 from trivalent to bivalent OPV to reduce type 2 vaccine-derived risks. IPV is used in many countries and provides individual protection and helps prevent outbreaks when OPV circulation is limited.

Diagnosis is by isolation or detection of poliovirus RNA from stool or throat specimens; cerebrospinal fluid analysis and neuroimaging may accompany evaluation in suspected meningitis or paralysis. There is no specific antiviral treatment; management is supportive, focusing on reassurance, rehabilitation, and respiratory support if needed.

Public health status: The Global Polio Eradication Initiative, launched in 1988, dramatically reduced polio incidence worldwide. Endemic transmission now persists in a small number of countries, and vaccine-derived outbreaks have occurred in others, underscoring the need for ongoing immunization and surveillance.