#Influenza A Virus detection in Bulk Tank and Pen Level #Milk from #Dairies Affected by Highly Pathogenic Avian Influenza #H5N1
Abstract Highly pathogenic avian influenza virus H5N1 has been infecting dairy herds in the U.S. since its initial incursion into cows in early 2024 . Although national strategies have aimed to detect affected herds , the best way to surveil herds for the H5N1 virus has not been formally studied and we also do not understand herd-level patterns of infection . To understand infection patterns of H5N1 in dairy herds over time, we conducted early surveillance of non-affected farms in California in the Fall of 2024 in an observational study. Daily bulk tank milk (BTM) samples were submitted from each herd and tested for influenza A (IAV) via rRt-PCR. In a subset of herds, IAV testing of multiple excretion types from cattle of different classes and pen-level daily milk was also completed soon after BTM detection. Daily detections of IAV occurred in BTM for a minimum of 33 days , with some herds continuing to have detection beyond a 75-day window. BTM Ct nadirs were seen between 1-3 we...