Influenza A(H5) in wastewater specimens collected in Portland on July 22 and 24, 2026, indicate the presence of highly pathogenic avian influenza virus A(H5N1) (HPAI) in Maine. The specimens were collected as part of routine wastewater surveillance operations, and subsequent testing did not identify influenza A(H5), suggesting time-limited or intermittent exposure (see WastewaterSCAN Dashboard). Wastewater comes from many sources, and detection could indicate a virus is present in animal, animal-product, and/or human sources. Wastewater testing cannot distinguish the origin of a pathogen detection. Local environmental data suggest infected wild birds may have contributed to this detection.
No human HPAI infections have been reported in Maine or other Northeast states in recent months. It is unlikely these detections are due to infection in humans. Human exposures to, and infection with, HPAI through animals and the environment remain a possibility.
Clinicians are advised to:
- Assess for relevant exposure history in patients with clinically-compatible respiratory illness
- Test for influenza in patients with compatible illness
- Send all influenza A positive specimens to Maine Health and Environmental Testing Laboratory (HETL) for subtyping when seasonal influenza virus activity is minimal