Tracking poliovirus through wastewater: environmental surveillance insights from Haïti (2020–2023)

Environmental surveillance (ES) for poliovirus is a critical component of global eradication efforts, enabling the detection of virus circulation in communities, even in the absence of acute flaccid paralysis (AFP) cases. To monitor poliovirus circulation in a high-risk setting, ES was established in 2016 in Haïti in two cities (Port-au-Prince and Gonaïves) and expanded to five cities, adding Saint Marc, Cap Haïtien, and Port-de-Paix by 2023. Wastewater samples were collected monthly from 13 sites in urban areas and processed at CDC-Atlanta using the concentration and filtration elution (CaFÉ) method developed to concentrate enteroviruses, including polioviruses. Virus isolation was performed using poliovirus-sensitive (L20B) cells and enterovirus-sensitive (RD) cells, followed by molecular detection screening via real-time reverse transcription PCR designed for enterovirus and poliovirus typing. Between 2020 and 2023, sporadic Sabin-like poliovirus vaccine strains of serotypes 1 and 3 were detected, and no wild poliovirus (WPV) or vaccine-derived poliovirus (VDPV) was identified. The overall enterovirus detection rates ranged from 36% to 91% in 2020, 12% to 58% in 2021, 16% to 60% in 2022, and 27% to 73% in 2023, with some detection rates at some sites much lower than the optimal 50% target for global ES sites. Based on the lower detection rate, used as the main quality indicator for optimal ES, two sampling sites were discontinued in 2023 (one in Saint Marc and one in Cap Haïtien). The findings underscore the importance of high-performing ES in high-risk regions to augment AFP surveillance and serve as an early warning indicator of poliovirus circulation.IMPORTANCEPoliovirus environmental surveillance (ES) is a critical tool for detecting virus circulation before symptomatic cases of acute flaccid paralysis occur, especially in areas with inadequate surveillance. Haïti, a high-risk country for poliovirus transmission, faced numerous challenges from 2020 to 2023 that impacted ES operations, including political instability, humanitarian crisis, and site closures. This study provides a comprehensive evaluation of ES performance during that period, offering insights into surveillance resilience and sustainability in low-resource settings. The findings are timely and relevant, particularly in the context of the recent circulating vaccine-derived poliovirus type 2 (cVDPV2) outbreaks in Europe and Africa, and contribute to optimizing ES strategies globally to support polio eradication efforts.