Detecting Influenza A Viruses in Surface Water: A Comparison of Passive Sampling to USEPA Method 1615

Abstract

Climate change, urbanization, and agricultural intensification are increasing the risk of viral contamination in surface waters, which act as reservoirs and transmission pathways for waterborne viruses. Influenza A (INFA), specifically, avian influenza strains, carried primarily by wild waterfowl, pose significant threats to animal, human, and economic health, making freshwater environments optimal for early surveillance. This study evaluated the performance of granular activated carbon (GAC)-based passive samplers paired with reverse transcription quantitative polymerase chain reaction (RT-qPCR) for detecting INFA, avian influenza H5, and pepper mild mottle virus (PMMoV) genes in lakes and rivers across Nova Scotia. Passive samplers were deployed weekly at four lakes and one river, with INFA concentrations ranging from 1.7 × 104 to 5.6 × 1012 GC sampler-1 and H5 from 6.2 × 104 to 1.8 × 1011 GC sampler-1. PMMoV was detected at two sites. Detection frequency corresponded with fall migration and waterfowl presence, while emphasizing the influence of wildlife, agriculture, and wastewater inputs. When compared to an adapted USEPA Method 1615 (electropositive filtration), GAC based passive sampling displayed comparable INFA detection, detected H5 where filtration did not, and missed PMMoV detections captured by filtration. Field and bench-scale analyses of NanoCeram filtration indicated no significant difference in detection across tested flow rates (4, 7, 10 LPM) and volumes (84.6 to 360 L). These findings highlighted the strong potential of GAC-based passive sampling as a feasible and complementary tool for avian influenza surveillance in freshwater systems.