The U.S. Department of Agriculture announced Friday that lactating dairy cattle moving interstate from states with no detected H5N1 will no longer require pre-movement bird-flu testing. [1] Idaho confirmed five additional infected herds in the prior month; the B3.13 genotype identified in Idaho dairies matches detections in alpacas and poultry, and the state veterinarian's multi-factor finding ruled out migratory birds without naming the operative vector. [2]

The paper's Saturday read treated the wild-bird ruling-out as a state-vet finding rather than epidemiology speculation. The vector — vehicle, feed, equipment, person, or shared milking infrastructure — has not been named. USDA's testing rule has now loosened before any of those identifications has been made public.

The administrative geometry is the news. Federal counterparties usually tighten as state findings narrow; this week, Idaho narrowed and Washington widened. The unaffected-state carve-out depends on a national-surveillance picture that is itself thinning out: Forest Service, NSB, MMWR queue. The CDC dashboard for H5N1 in dairy still reports state-level case counts; Idaho's cluster will not move on Sunday's update because the testing rule is what changed, not the genotype.

A pathogen that has crossed from poultry to cattle to alpacas is not the kind that rewards a federal step back at the moment a state cannot identify how it travels.

-- KENJI NAKAMURA, Boise