Genotypic Characterisation of Poliovirus Isolates from Acute Flaccid Paralysis Cases in Zamfara State

Despite Nigeria's declaration of wild poliovirus eradication in 2020, circulating vaccine-derived poliovirus (cVDPV) strains continue to cause acute flaccid paralysis (AFP) outbreaks, particularly in under-vaccinated communities in the North West geopolitical zone. This study characterises poliovirus genotypes isolated from AFP cases reported in Zamfara State between 2022 and 2024, using specimens archived in the WHO-accredited National Polio Laboratory in Lagos. A retrospective laboratory-based study will retrieve AFP stool specimen records for Zamfara State from the GPEI-supported national AFP surveillance database. Viral isolation records and VP1 gene sequencing data will be analysed to determine poliovirus type, origin (Sabin-like versus vaccine-derived), and genetic distance from reference strains. The spatial distribution of cases across local government areas and vaccination coverage data from the National Immunisation Plus Days will be overlaid to identify community-level immunity gaps. Recent GPEI reports document persistent cVDPV2 transmission in Zamfara linked to low oral polio vaccine coverage and population movement. Findings will describe the molecular epidemiology of poliovirus in Zamfara State, contributing to outbreak investigation reports for the WHO-UNICEF Emergency Operation Centre and supporting targeted supplemental immunisation activities. This study reinforces the importance of AFP surveillance in sustaining Nigeria's polio-free status. Keywords: poliovirus, vaccine-derived poliovirus, acute flaccid paralysis, Zamfara State, genotypic characterisation