Human poliovirus type 1 (PV1) is one of the three serotypes of poliovirus that can cause poliomyelitis, a highly contagious viral infection affecting humans. Poliovirus is an enterovirus, belonging to the Picornaviridae family. It is a non-enveloped, single-stranded positive-sense RNA virus.
Poliovirus is primarily transmitted through the fecal-oral route or, less frequently, by ingestion of contaminated water or food. The virus initially infects the cells lining the throat and intestines, where it replicates. In most cases, poliovirus infection is asymptomatic or causes mild, flu-like symptoms. However, in approximately 0.5% of cases, the virus can spread to the central nervous system, particularly the spinal cord and brainstem, leading to paralysis or even death.
PV1 is the most virulent and widespread of the three poliovirus serotypes. It is responsible for the majority of paralytic polio cases worldwide. The other two serotypes, PV2 and PV3, are less virulent and have been declared eradicated.
The development of effective vaccines has been instrumental in controlling and preventing polio. There are two types of polio vaccines:
- Inactivated poliovirus vaccine (IPV): Developed by Jonas Salk in the 1950s, IPV is based on inactivated (killed) poliovirus and is administered via intramuscular injection. IPV induces a strong antibody response, providing protection against all three serotypes of poliovirus without the risk of vaccine-associated paralytic poliomyelitis (VAPP).
- Oral poliovirus vaccine (OPV): Developed by Albert Sabin in the 1960s, OPV is a live, attenuated vaccine administered orally. OPV is highly effective in providing both individual and community immunity due to its ability to spread from vaccinated individuals to unvaccinated contacts. However, in rare cases, OPV can revert to a neurovirulent form, causing VAPP or circulating vaccine-derived polioviruses (cVDPV).
Ongoing global efforts, such as the Global Polio Eradication Initiative (GPEI), aim to eradicate all serotypes of wild poliovirus, including PV1. As a result of widespread vaccination campaigns, the number of polio cases has decreased dramatically worldwide, and the disease is now endemic in only two countries: Afghanistan and Pakistan. The complete eradication of polio would make it the second human disease, after smallpox, to be eradicated.