Trends and Outcomes of Wastewater Surveillance for Poliovirus and Enterovirus in Nigeria, 2023–2025

Background: Wastewater-based environmental surveillance (ES) is a core component of the Global Polio Eradication Initiative, complementing acute flaccid paralysis (AFP) surveillance by enabling early detection of poliovirus circulation at community level. Nigeria maintains one of the largest ES networks in Africa due to its historical risk of poliovirus transmission.
Methods: This descriptive analysis reviewed national ES data from 2023 to 2025, covering 36 states and the Federal Capital Territory. Monthly wastewater samples (bi‑monthly in high‑risk states) were processed using WHO‑recommended virus isolation and intratypic differentiation protocols. Key indicators included sample volume, enterovirus (EV) detection rate, and poliovirus isolation outcomes.
Results: In 2025, 1,066 wastewater samples were collected from 92 ES sites nationwide. Of these, 389 (36.5%) were negative, 364 (34.1%) yielded non‑polio enteroviruses, and 132 (12.4%) contained Sabin‑like polioviruses. Thirteen samples (1.2%) were confirmed as circulating vaccine‑derived poliovirus type 2 (cVDPV2), predominantly from Borno, Zamfara, Taraba, and Kebbi states. National EV detection rates increased from 49.6% in 2023 to 67.2% in 2024, before declining to 61.3% in 2025. Surveillance intensity was highest in bi‑monthly sampling states, notably Sokoto and Zamfara.
Conclusion: Nigeria’s ES system remains a sensitive and indispensable tool for poliovirus detection, revealing ongoing cVDPV2 transmission in selected northern states. Sustained investment in sampling quality, laboratory capacity, and genomic sequencing is essential to preserve surveillance sensitivity and guide timely outbreak response.