The socio-economic shield limits Lassa virus spillover in urban West Africa.

Abstract

Spatial risk models for Lassa fever (LF) generally predict the primary reservoir, Mastomys natalensis, is restricted to rural landscapes. This study integrates multispecies biotic interactions and anthropogenic land-use into a high-resolution framework to evaluate LF's urban potential. I implemented an integrated multispecies occupancy model to reconstruct the reservoir's realized niche, accounting for sampling bias and invasive rodent competitors. A socio-economic filter, proxied by night-time lights, was introduced to model the dampening effect of urban infrastructure on spillover. Annual infections were estimated using a demographic compartmental model incorporating empirical seroreversion rates. Results indicate high biological hazard across the peri-urban fringes of major West African cities. However, an infrastructure-driven socio-economic shield decouples this hazard from human incidence in dense urban cores. Accounting for spatial shielding and antibody waning yields an estimated 2.6 million annual Lassa virus infections. Comparing predictions to clinical data reveals substantial surveillance gaps, identifying highly suitable silent districts in Nigeria, Benin, and Togo with zero reported cases. LF possesses the biological potential to become a peri-urban disease; addressing these surveillance gaps at the peri-urban interface is a critical public health priority.