The Departamento of Agricultura, Comércio, and Proteção to the Consumidor of Essa detection, announced on December 14, 2025, marks the first occurrence of the disease in dairy cattle in the state. The collected samples were analyzed by Laboratório of Diagnóstico Veterinário of Wisconsin and confirmed by the USDA’s Laboratórios Nacionais of Serviços Veterinários.
The affected farm was immediately quarantined to contain the spread of the virus. Animais who show clinical signs will be isolated and receive additional treatment. The DATCP coordinates actions with the Departamento of Agricultura of the Estados Unidos (USDA), the Administração of Alimentos and Medicamentos (FDA) and the
There is no indication that the herd has recently received new animals, and the cows did not exhibit obvious symptoms prior to detection through routine milk testing.
Immediate response measures
State and federal authorities are working together to monitor the situation in Dodge County. The quarantine prevents the movement of animals from the affected property. The USDA reinforces that the commercial milk supply remains safe because pasteurization inactivates the H5N1 virus.
Producers receive guidance to reinforce biosafety protocols on their farms. DATCP maintains direct communication with registered breeders for updates on outbreaks.
Clinical signs in dairy cattle
The main symptoms observed in infected livestock include reduced feed consumption and decreased stomach movements. Há also reports of a significant drop in milk production across the herd.
- Changes in the consistency of manure, often dry or sticky;
- Increase in milk conductivity;
- Affected cows may have zero milk production in more severe cases.
These signs help producers to identify possible infections early and report them to authorities.
National context of the outbreak
H5N1 has been circulating in the Estados Unidos since 2024, with initial detections in dairy herds in the Texas and Kansas in March of that year. Desde then, the virus affected properties in several states, including Califórnia, Idaho and Michigan.
Wisconsin has participated in USDA’s Estratégia Nacional of Testagem of Leite since May 2025, with samples collected monthly. Detection in Dodge occurred during this routine surveillance, with no apparent symptoms in the herd.
The virus is spread mainly by migratory wild birds, which transmit to domestic mammals.
Recommended biosecurity
Dairy cattle and poultry breeders must register their properties with DATCP, as per state legal requirement. Registration facilitates quick communications during health emergencies.
Authorities encourage daily monitoring of animal health and the adoption of strict biosecurity practices. Isso includes farm access control and equipment cleaning.
- Limitation of contact with wild birds;
- Separation of sick animals;
- Use of personal protective equipment by workers.
Reports of suspicious signals should be made immediately to DATCP at (608) 224-4872 or after hours at (800) 943-0003.
Public health risk
The CDC classifies the risk of H5N1 to the general population as low at Estados Unidos. Casos humans occur sporadically, associated with direct contact with infected animals.
Pasteurization completely eliminates the virus in processed commercial milk. Leite of sick animals is diverted or discarded, not entering the supply chain.
Dairy farm workers in close contact with livestock receive health monitoring by local authorities.
Continuous surveillance in the state
Wisconsin has implemented mandatory testing for Influenza A in dairy cattle moving interstate. The national milk testing strategy in silos contributes to early detection.
The state remained free of cases in dairy cattle until December 2025, despite occurrences in commercial and wild birds. The rapid response to detection in Dodge aims to prevent spread to other herds.
Producers receive financial support from the USDA for biosecurity measures and compensation for production losses.
Evolution of the virus in mammals
H5N1 has adapted to mammals since its global expansion in birds from 2022. Detecções in dairy cattle reveals efficient transmission in cows, with impacts on production.
Research indicates that the virus causes mild symptoms in most cattle cases, unlike the high mortality in birds. Genomic surveillance monitors possible mutations.
Federal authorities are investing in vaccination strategies for poultry and livestock, although they are still in the development phase.
The outbreak reinforces the importance of early detection systems, such as those implemented in Wisconsin since 2024.
