Tracking enterovirus and poliovirus circulation in Parma: Environmental surveillance from 2019 to 2024

Background and aim: Environmental Surveillance (ES), which gained renewed interest during the COVID-19 pandemic due to its effectiveness in the early detection of viral spread, has long been recognized as a critical component of the Global Polio Eradication Initiative. This approach has historically played a fun-damental role in the early identification of poliovirus transmission and remains an essential tool for monitor-ing the circulation of enteroviruses, underscoring its enduring significance in public health surveillance. This study aims to present six years ES data on poliovirus and enterovirus in Parma, Italy. Methods: The samples were collected every two weeks at the inlet of two sewage treatment plants and underwent a WHO protocol analysis. We detailed the temporal and spatial distribution of non-polio enterovirus (NPEV ) and poliovirus based on the virus cultures algorithm from 2019 to 2024. Results: A total of 228 sewage samples were col-lected, a median of 44 samples per year. 68.9% resulted in positive cell cultures, without significant differ-ences among the two treatment plants. The year 2023 had the highest percentage of NPEV isolates (97.7%), followed by 2024 and 2022 (87% and 70.5% respectively). 2021 had the overall lowest positive (35.6%). One Sabin-like strain type 3 was detected in 2022. Seasonal time trends were observed. Conclusions: This study contributes to a better understanding of NPEV circulation patterns in a pandemic and post-pandemic period, underlining the importance of ES as a tool in the assessment of the epidemiological spreading of enterovi-ruses and significantly poliovirus.