Utah mink farm bird flu outbreak linked to cattle strain by virologists
A virulent bird flu strain has infected thousands of mink at C&T Fenn Farms in Utah for more than two months, according to ProPublica.
- Ten whole-genome sequences analyzed by virologists belong to the B3.13 cattle-adapted lineage, linking the outbreak directly to the strain circulating in U.S. dairy herds since March 2024.
- State and federal authorities have declined to order a mass cull or mandate routine testing for farm workers despite one individual exhibiting classic avian influenza symptoms.
- Every analyzed mink virus carries the PB1 K388R mutation and the PB2 M631L cattle mutation, which is known to enhance viral replication in mammalian hosts.
Unregulated Mink Outbreak in Utah
Public health experts characterize the situation at the Utah fur farm as an ideal environment for viral adaptation during active human influenza season. Unlike poultry operations where a single positive avian influenza test mandates government-ordered culling, federal regulations do not govern mink farms. Utah state veterinary officials declined to order a cull at C&T Fenn Farms and bypassed site visits, relying instead on telephone calls and mapping software, according to ProPublica’s investigation.
Cattle-Adapted B3.13 Lineage Detection
Genomic analysis of ten whole-genome sequences revealed they belong to the B3.13 cattle-adapted lineage originating from Texas dairy herds, as discussed by virologists Rich Condit and Alan Dove on the podcast This Week in Virology.
Every analyzed mink virus features a shared PB1 K388R mutation—a genetic change previously documented in Spanish mink in October 2022—alongside the pre-existing PB2 M631L mutation that increases mammalian replication capacity.
Utah Officials Ignore Safety Guidance for Farm Workers
Utah officials agreed not to actively monitor or routinely test farm workers despite Centers for Disease Control and Prevention guidance and a worker showing a classic bird flu symptom. Marc Johnson, a virologist at the University of Missouri, told The Telegraph that workers continue entering the mink facility during active human flu season, creating conditions ripe for new viral recombinants. The Telegraph also reported that the Trump administration has faced criticism for losing control of the broader H5N1 spread across mink and cattle farms, having previously canceled a $766 million contract with Moderna for human H5N1 vaccine development.
Disclaimer: The information provided in this article is for educational and scientific communication purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider regarding any medical condition, diagnosis, or treatment plan.