Avian Influenza: Lakes and Rivers at the Crossroads of Viral Circulation

Avian influenza is primarily monitored in poultry flocks and among wild birds. A thesis defended at Dalhousie University in Canada proposes tracking the circulation of influenza viruses directly in surface waters. The study compares a passive sampling method to the U.S. Environmental Protection Agency’s (US EPA) reference filtration technique.   The approach is based on a simple idea. Waterfowl, major reservoirs of avian influenza, spread the virus throughout their environment. Lakes, rivers, and wetlands thus serve as crossroads where wildlife, human activities, and poultry farms intersect. Monitoring these environments is an attempt to detect a signal before visible outbreaks occur. Rather than periodically sampling large volumes of water, the study tests passive sensors made of granular charcoal, which are submerged for several days and then analyzed by RT-qPCR. This quantitative reverse transcription PCR (qRT-PCR) method allows for measuring contamination over time, given that viral concentrations can fluctuate significantly. Three targets were investigated: influenza A, an H5 marker, and the pepper mottle mosaic virus (PMMoV), a human fecal marker used as an indicator of human-derived water contamination. Deployed in four lakes and one river in Nova Scotia, the sensors revealed variable viral concentrations, but these were consistent with the presence of waterfowl and the migration season. High levels of the H5 virus were detected, sometimes in locations where the standard filtration method yielded negative results. Conversely, certain markers were more effectively captured by filtration than by passive sampling. The lesson to be drawn from this study is less technological than strategic. Environmental surveillance does not replace conventional veterinary measures, but it can complement them by documenting viral circulation before clinical cases emerge. However, health protocols must be standardized, and these molecular signals must be linked to actual disease dynamics. This research serves as a reminder that the virus also circulates outside the usual detection systems. In water, silently, it sometimes leaves traces that are worth measuring.