A retrospective analysis reveals that H5 avian flu surfaced in Oregon wastewater weeks before the state’s first outbreak in poultry and wild birds and 2 years before the first outbreak in US cattle.
A team led by Oregon State University researchers evaluated 551 influenza A virus–positive wastewater samples from 20 sites from September 2021 to July 2024.
In January 2022, H5N1 clade 2.3.4.4b virus was first identified in wild birds in the United States. In Oregon, the clade was first detected in wild birds and poultry in May 2022.
“Interpretation of avian influenza A(H5) subtype detections in wastewater requires an understanding of human and animal contributors to the sewershed because current testing does not distinguish between human and animal sources,” the authors wrote. “Potential animal contributors include wild birds, farms with poultry or dairy cattle outbreaks, and dairy processing facilities.”