USDA
US Department of Agriculture; regulates dairy and poultry disease surveillance, including H5N1 mandatory testing.
USDA ended mandatory H5N1 testing of dairy cattle moving between states on 1 May 2026, the day Idaho confirmed its first infected herd; twelve days later Idaho had 59 herds under quarantine.
Last refreshed: 4 October 2026 · Appears in 1 active topic
Why has USDA not updated its dairy-worker guidance since the aerosol study?
Timeline for USDA
Suspended live Mexican cattle imports in 2025
Pandemics and Biosecurity: Mentioned in: Screwworm cases in Mexico rise fivefoldMentioned in: CDC cuts bird-flu reports to monthly
Pandemics and BiosecurityTracked and confirmed 59 quarantined herds and 86 individual cattle positive for H5N1 in Idaho
Pandemics and Biosecurity: Idaho dairy H5N1: 1 to 59 herds in twelve daysEnded mandatory pre-movement H5N1 testing for lactating dairy cattle moving interstate from states without confirmed HPAI outbreaks, effective 1 May 2026
Pandemics and Biosecurity: USDA ends mandatory H5N1 interstate cattle testsMentioned in: Idaho dairy H5N1 breaks five-month US lull
Pandemics and BiosecurityBackground
The US Department of Agriculture is the federal department for farming, food safety and rural development, with a budget of roughly $200bn a year. Its Animal and Plant Health Inspection Service (APHIS) regulates livestock disease. APHIS can order mandatory testing and restrict the movement of infected herds, and it runs The National tracker for highly pathogenic avian influenza in poultry and dairy cattle. USDA shares the federal H5N1 dairy response with CDC and FDA.
APHIS imposed its H5N1 testing order on dairy herds in 2024, requiring lactating cows to test negative before crossing state lines, and lifted it on 1 May 2026. Since 2025 USDA's animal data has sat on a tracker separate from CDC's human case page, so states must match animal and human detections across two federal sources.
USDA also holds the US line against New World screwworm. The United States eradicated the fly in the 1960s by releasing billions of sterile males, and in 2025 USDA suspended imports of live Mexican cattle as the parasite moved north. By 18 September Mexican health data showed 575 human infestations in 2026, up from 117 in all of 2025.
USDA dropped its cattle movement tests
On 1 May 2026 USDA's Animal and Plant Health Inspection Service ended the mandatory H5N1 test for dairy cattle crossing state lines. APHIS said its milk surveillance network made movement testing redundant. The same day Idaho confirmed its first infected herd, ending a five-month gap in US dairy detections.
The rollback left the department defending a gap during a surge. By 12 May Idaho had 59 quarantined herds across four counties and 86 confirmed cattle, and the virus had reached cats in Washington and Oregon and alpacas in Idaho. When CDC cut its bird-flu reports to monthly on 29 May, two federal surveillance layers had thinned in one month. USDA's dairy-worker guidance also stayed tuned to contact spread after an Emory study found the virus in submicron aerosol in milking parlours.
Why has the USDA not updated dairy-worker PPE guidance after the aerosol study?
What is USDA doing about H5N1 in dairy cattle?
Where can I find the USDA H5N1 dairy herd detection data?
