On Feb. 27, 2025, research from Oregon State University (OSU) showed that wild birds can account for much of the avian influenza virus evidence found in wastewater in Oregon, suggesting wastewater detections of the virus do not automatically signal human, poultry or dairy cattle cases of bird flu.

The study, led by Tyler Radniecki, a professor in OSU’s College of Engineering, and collaborators at OSU, the Oregon Health Authority and the Oregon Department of Agriculture analyzed nearly three years of wastewater surveillance across 20 communities in the state. The researchers looked at the new clade of avian influenza virus that first appeared in the United States in January 2022 and by the end of 2024 had infected poultry and cattle throughout the country.

Detections of the avian influenza H5N1 H5 subtype were most frequently found in or near communities with important wild bird habitats, the authors note. There was no association between H5 subtype detections in wastewater and outbreaks of infected poultry, or the location of dairy farms or dairy processors.

Throughout the outbreaks, wastewater surveillance has been used by the Centers for Disease Control and Prevention (CDC) and state and local health departments as a monitoring tool, the researchers say. However, they add, interpretation of H5 in wastewater is complex because current testing practices do not distinguish between animal and human sources. The study was published in Morbidity and Mortality Weekly Report, a journal of the CDC.