With fall migration season approaching, when wild birds may spread the virus across new areas, maintaining strict farm-level biosecurity, prompt disease reporting, and cross-agency coordination remain the most effective tools to protect both animal and human health.
A fresh outbreak of highly pathogenic avian influenza (HPAI H5N1) in Jefferson County, Wisconsin, is raising alarms across the region’s poultry and dairy industries. The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) confirmed the detection on Sept. 25, 2025, in a commercial poultry flock exceeding three million birds—the state’s largest single outbreak this year and its first since April.
This incident is part of a recent uptick in H5N1 cases in Midwestern states and comes amid ongoing nationwide efforts to monitor and contain the virus in both poultry and, increasingly, dairy cattle. Wisconsin officials report that the affected Jefferson County farm is under quarantine, all birds on the premises will be culled to prevent further spread, and a 10-kilometer control zone has been established around the site.
A Broader National Context
According to the U.S. Department of Agriculture (USDA), 21 new poultry outbreaks were confirmed across eight states in the past 30 days, alongside a single detection in livestock. Although H5N1 infections in dairy cattle have been reported in other states, Wisconsin has so far avoided detections in its herds.
To bolster defenses against such incursions, Wisconsin’s dairy sector has been participating in the USDA Animal and Plant Health Inspection Service (APHIS) National Milk Testing Strategy. Earlier this month, DATCP announced that Wisconsin achieved “Gold Status” for its statewide monthly milk sampling and testing program—screening more than 18,000 samples with no H5N1 detected to date.
Safeguarding Public and National Health
While the current public health risk from H5N1 remains low, Wisconsin’s Department of Health Services (DHS) and Jefferson County Public Health are actively monitoring exposed farm workers for any signs of illness. This includes direct symptom checks and the provision of guidance on appropriate use of personal protective equipment (PPE) for anyone in close contact with poultry. The Centers for Disease Control and Prevention (CDC) continues to recommend the use of gloves, masks, and protective clothing, along with strict hand hygiene and disinfection protocols, for agricultural workers handling birds or livestock.
For the general public, outbreaks like this underscore the importance of strong animal disease surveillance and biosecurity as pillars of national health security. Rapid detection and containment in animal populations reduce the risk of food supply disruptions, economic losses, and zoonotic spillover events that could threaten both public health and the nation’s agricultural economy.
Coordinated Response and Reinforced Biosecurity
DATCP, in coordination with USDA APHIS, has taken several immediate steps to contain the Jefferson County outbreak:
- Quarantine and Movement Restrictions: Affected premises are quarantined, and movement of live poultry, poultry products, feed, and equipment within a 10-kilometer control area is strictly regulated.
- Depopulation and Disposal: All birds on the infected farm—over three million—will be humanely depopulated, with disposal conducted according to state and federal environmental guidelines to minimize contamination risks.
- Enhanced Surveillance: Flocks within the control and surveillance zones are subject to increased testing and on-site inspections by veterinary staff. Producers can use DATCP’s online mapping tool to check if they fall within an active zone.
- Worker Health Monitoring: DHS and local health departments are providing active monitoring and guidance to farm workers who may have been exposed.
- Biosecurity Reinforcement: DATCP continues to urge all poultry and livestock owners statewide to wash hands before and after contact with animals, disinfect tools and vehicles, restrict visitor access to barns, keep birds indoors when possible, and isolate new or returning animals for at least 30 days.
- Premises Registration: Producers are reminded that state law requires all livestock premises to be registered to facilitate rapid communication during disease events.
State and federal officials stress that birds from the affected Jefferson County flock will not enter the food supply. Consumers are advised that properly handled and cooked poultry products remain safe to eat.
Challenges and Next Steps
The Jefferson County outbreak also highlights several persistent challenges in national and state-level preparedness:
- Wild Bird Surveillance Gaps: Monitoring of migratory waterfowl—key carriers of H5N1—remains patchy, limiting early-warning capabilities during seasonal migrations.
- Uneven Biosecurity Compliance: Smaller or resource-limited farms often struggle to meet recommended biosecurity standards, such as keeping flocks indoors or maintaining controlled access points.
- Resource Strain for Rapid Response: Humane culling and safe disposal of millions of birds requires substantial logistical support and can overwhelm existing veterinary and environmental resources.
- Human Health Integration: Worker health monitoring is largely reactive and not yet standardized across facilities; data sharing between animal and public health agencies can be slowed by siloed systems.
- Testing and Enforcement Limitations: While Wisconsin’s dairy sector has excelled in milk testing, national testing frequency is being scaled back in some states after initial benchmarks were met, raising concerns about missed low-level infections.
Addressing these gaps will require sustained funding, stronger interstate coordination, and expanded outreach to ensure smaller producers and farmworkers receive timely support, PPE, and training. Long-term improvements in wild bird and environmental surveillance, workforce surge capacity for depopulation and testing, and integrated animal-human data systems will be essential to reduce the scale of future outbreaks.