Dairy cattle movement networks govern the spread and persistence of H5N1 B3.13 in the United States

Avian influenza H5N1's B3.13 strain surfaced in U.S. dairy cattle in March 2024, leading to the biggest known outbreak among mammals. By matching genomic data with the flow of cattle, researchers discovered that live cattle transport is the main reason the virus spreads across the nation, not wild or domestic birds. An analysis indicates that 40% of cross-state viral transmissions occurred before B3.13's first identification, while 70% had taken place before April 2024 when dairy cattle movement restrictions were put in place.

However, despite these restrictions, transmission within states continued, fueled by the density and volume of cattle movement. Simulations suggest that the connectivity of counties near the Texas Panhandle, the site of the initial cases, made the region prone to become an outbreak hub. If interstate movement restrictions had been implemented 2-3 months earlier, the epizootic might have been significantly mitigated, as the spread had already been happening secretly before the detection.

Network-focused measures were more effective than location-based containment, but the key to successful intervention in the models was the speed of response, not the strength of the intervention. This emphasizes the need for surveillance systems that can detect the emergence of pathogens before they spread widely.