Integrated Determinants of Persistent Wild Poliovirus Transmission in Pakistan and Afghanistan: The Roles of Cross-Border Mobility, Hard-to-Reach Populations, and Micro-Transmission Hotspots, 2010-2025

BACKGROUND: Wild poliovirus type 1 (WPV1) remains endemic in Pakistan and Afghanistan, the last global reservoirs of the virus. Despite a reduction in global incidence since 1988, persistent transmission in these two countries continues to undermine eradication efforts. This study provides an integrated assessment of determinants sustaining WPV1 transmission between 2010 and 2025, focusing on cross-border mobility, immunity gaps in hard-to-reach populations, and localized micro-transmission hotspots. METHODS: A scoping review was conducted in accordance with PRISMA-ScR guidelines. Literature published between 2010 and 2025 was searched across PubMed, Embase, Scopus, Web of Science, and WHO/GPEI repositories. RESULTS: Findings demonstrated that genomic and phylogenetic evidence confirmed Pakistan and Afghanistan as a single epidemiological block, with more than 85% of isolates showing cross-border genetic linkage. Immunity gaps persisted among nomadic, displaced, and conflict-affected children, where routine coverage ranged 22-41% and seroprevalence fell below 70%. Environmental surveillance identified 12 persistent hotspots, with year-round WPV1 detection in Karachi, Peshawar, Quetta, and Kandahar. Operational constraints, including campaign delays, insecurity, and funding shortfalls, were consistently associated with higher case counts and reduced surveillance sensitivity. CONCLUSION: The continuation of WPV1 in Pakistan and Afghanistan reflects a convergence of factors—cross-border movement, immunity gaps among marginalized groups, and entrenched transmission hotspots exacerbated by operational challenges. Public health implications include the urgent need for synchronized cross-border campaigns, targeted strategies for mobile and marginalized groups, strengthened surveillance, and sustained financing. Rapid interruption of WPV1 in this corridor is essential not only for eradication but also to end the escalating cVDPV2 emergency.