Systematic testing of wastewater can detect and monitor emerging pathogens, including highly pathogenic avian influenza (HPAI) A (H5) during the current outbreak in the US. Interpretation of influenza A (H5) detections in wastewater is complex because current methods do not distinguish between human and animal contributors. Influenza A (H5) has been detected in wastewater adjacent to dairy cattle outbreaks, likely due to dairy processing discharge. Poultry outbreaks and wild birds may also contribute to influenza A (H5) in wastewater.