Hot topic: Epidemiological and clinical aspects of highly pathogenic avian influenza H5N1 in dairy cattle

On March 24, 2024, the US Department of Agriculture (USDA) confirmed the first case of highly pathogenic avian influenza (HPAI) H5N1 clade 2.3.4.4b in dairy cattle. Following this initial detection, the virus was found to have spread to other species, including humans. Since then, at least 192 dairy herds across 13 states have tested positive for the virus. The emergence of HPAI H5N1 in dairy cattle poses a serious threat to the dairy industry, requiring an approach that integrates human, animal, and environmental health. Enhancing biosecurity, improving surveillance, and advancing research are critical to managing this challenge. Swift adaptation is needed to protect both public health and dairy production. Through this work, we discuss the epidemiological and clinical aspects of HPAI H5N1 in cattle by reviewing the spatiotemporal situation of the disease across the United States, the clinical signs and testing leading to a confirmed case, and the surveillance and control measures implemented at the national and state levels. Further, considering pathogenesis and risk factors, we discuss surveillance and control measures to implement within herds, and note areas where research is needed to understand how to control this emerging disease.