| Popis: |
Poliovirus (PV) belonging to the Picornavirus genus, Picornaviridae family, is ribonucleic acid (RNA) virus, the leading cause of neurological diseases and disability in developing countries. New infections typically attributed to emerging and reemerging RNA viruses that have expanded their geographic range contributing to the burden of disease. This is what prompted the World Health Assembly in 1988 to adopt the goal of global polio eradication through intensive use of the trivalent oral polio vaccine (OPV). Wild PVs (WPVs) became endemic in only four countries. Between 2000 and 2005, there were six reported cases of poliomyelitis due to circulating vaccine-derived PV (VDPV) (cVDPV) in China, Philippines, Madagascar, Haiti, Cambodia, Indonesia, and the Dominican Republic. In China, the viruses involved had been recombined with human enterovirus species C (HEV-C). All indigenous WPVs, or at least those of the same serotype as VDPVs, have been eliminated in countries or regions where these outbreaks have occurred, suggesting a decrease in the natural immunity of the population. Factors, such as low population immunity, circulation of HEV-C, and the absence of WPV of the same VDPV serotype, appear to be associated, in most cases, with the vaccine-derived strains emergence. Eradication of PV is undermined by the ability of attenuated live vaccine strains to return to virulence during the prolonged period of gastrointestinal replication. During replication in humans, OPV strains frequently (mutually adapt to new hosts) modify their genomes by recombination, which can sometimes result in vaccine-related paralytic poliomyelitis and the emergence of poliomyelitis epidemics associated with cVDPV. |
