Highly pathogenic avian influenza (HPAI) viruses of genotype B3.13 were first reported in dairy cattle in March 2024 and, by 4 March 2025, had infected at least 989 cattle herds in 17 states in the US (https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/hpai-confirmed-cases-livestock; accessed on March 24, 2025). Importantly, spillover infections of poultry and mammalian species, including cats and humans, have occurred (https://www.cdc.gov/bird-flu/situation-summary/index.html; accessed on 4 March 2025). Texas reported several infected herds in the spring and early summer of 2024 but saw fewer outbreaks during the second half of 2024, with reported outbreaks in July and December. Since September 2024, almost all reported outbreaks of genotype B3.13 viruses in dairy cattle have occurred in California. Here, we characterized self-submitted samples from a farm in Texas that experienced an outbreak in December 2024. This farm had purchased dairy cattle from several states in the US. We, therefore, asked whether the December 2024 outbreak in Texas was caused by B3.13 viruses that circulated undetected in dairy cattle or other species in Texas or resulted from the introduction of B3.13 viruses from California (having the highest number of affected farms at that time) or other states.