Idaho remains the country's H5N1 dairy hot spot with 25 herds confirmed across four counties — most heavily Gooding (34 herds reported by the state) and Jerome (17), with smaller clusters in Twin Falls (7) and Cassia (1) — yet the Idaho Department of Agriculture has still not named the index vector. [1] CIDRAP's running coverage notes that USDA, even as the cluster grows, continues to scale back interstate dairy testing requirements that were tightened a year ago for exactly this kind of cluster.

The Idaho genomes sequenced so far carry the B3.13 cattle clade, the same lineage now known to have crossed into an alpaca herd elsewhere in the state. [2] B3.13 is the genotype that established the cattle reservoir; without a named flyway link or wildlife trace-back, the public health story is that the virus is still moving and the diagnostic chain is being shortened, not the spread.

USDA's APHIS has continued to confirm individual herds case by case while the rule-making behind the broader testing regime softens. [3] Field veterinarians describe the practical effect as a "don't test, don't tell" posture — a phrasing already in circulation since the Texas cluster of 2024. The aperture between detection and reporting widens; the herd math keeps moving.

The more telling number is the silence. The trade rules are loosening at the same moment that a 25-herd state cluster has not produced a named vector — and the absence of a vector is exactly what loosened testing makes harder to find next time.

-- NORA WHITFIELD, Chicago