Invited review: The One Health challenges and opportunities of the H5N1 outbreak in dairy cattle in the United States

The outbreak of H5N1 in dairy cattle in the United States revealed challenges in identification and management of a novel disease. The virus showed an exceptional ability to spread between farms and among cows within a farm. The impact of the virus on dairy cattle varied from nonclinical to severe clinical signs and death. Many dairy producers did not report clinical signs in their cows or test for the virus. Cats and peridomestic birds on many affected dairies died from viral exposure. Dairy workers showed signs of conjunctivitis, which was confirmed to be due to H5N1. With the disease affecting multiple species and showing efficient cow-to-cow transmission, the situation only worsened. There was a negative impact on the relationships among dairy producers, dairy workers, poultry producers, and veterinarians, in which professional and personal relationships were severed and some experienced loss of employment. The regulatory response varied by geographic location, and in some states, animal health and human health authorities elevated producer fears of consequences of reporting. Authorities did quickly confirm that pasteurization inactivated the virus in dairy products and showed that it was very rarely detected in beef from affected cows. In this review, we will describe the relationships among the dairy industry and animal and human health and why the H5N1 outbreak requires a One Health perspective of all stakeholders in order to address it effectively.