NORTHEAST WISCONSIN – State and federal animal health officials have confirmed a case of highly pathogenic avian influenza (HPAI) in a commercial poultry flock in Jefferson County, according to the Wisconsin Department of Agriculture, Trade and Consumer Protection.
The affected site has been quarantined, and the flock will be depopulated to prevent further spread, DATCP said in a news release March 6.
Officials said birds from the operation will not enter the food supply.
Jefferson County is in the southeastern part of Wisconsin, positioned almost exactly midway between Madison and Milwaukee.
What is bird flu?
HPAI, commonly known as bird flu, is caused by the influenza A H5N1 virus.
The virus has circulated widely in wild birds across North America since 2021 and has triggered recurring outbreaks in both commercial and backyard poultry flocks.
In recent years, H5N1 has also been detected in U.S. dairy cattle, signaling a change in how the virus is spreading among animals.
Risk to the public remains low
According to the Centers for Disease Control and Prevention, the overall risk to the general public remains low. No evidence exists of sustained person‑to‑person spread of H5N1 in the United States, the CDC said.
Most human infections have occurred in people with close, unprotected contact with infected animals, including poultry and dairy cattle.
According to the CDC, of 71 total reported human cases of bird flu reported in the United States since February 2024, seven were detected through national flu surveillance and 64 were detected through human monitoring. Two of the 71 cases resulted in death.
Movement restrictions and biosecurity measures
DATCP has established a 6.2-mile control area around the infected Jefferson County premises, it said in its news release. The designation restricts the movement of poultry and poultry products in the area.
Livestock and poultry owners are being urged to strengthen biosecurity measures, including limiting access to animals, disinfecting equipment and keeping poultry separated from wild birds.
Steps residents can take
Health officials say residents in communities such as Fond du Lac, Manitowoc, Oshkosh, and Sheboygan can reduce their risk by:
People who work with poultry, livestock or wild birds should use appropriate protective equipment and monitor for symptoms such as eye irritation, cough or fever after potential exposure, officials said.
Reporting and ongoing monitoring
Anyone who notices unusual illness or increased deaths among birds or other livestock should report it to a DATCP district veterinarian.
State and federal agencies continue to monitor the situation and emphasize that Wisconsin’s food supply remains safe and closely regulated, the DATCP news release said.
For updates on how the H5N1 virus is affecting dairy cattle across the country, and to find resources on protecting Wisconsin dairy cattle, visit DATCP’s H5N1 in Dairy Cattle webpage at https://datcp.wi.gov/Pages/Programs_Services/AvianInfluenzaCattle.aspx.
A history of bird flu detections across Wisconsin
State and federal records show Wisconsin has dealt with repeated bird flu detections since 2022, affecting both commercial and backyard poultry flocks.
In recent years, cases have been confirmed in multiple counties, including Jefferson, Dane, Racine and Sheboygan, with quarantines later lifted.
In late 2025, officials also confirmed Wisconsin’s first H5N1 detection in a dairy herd, though agencies emphasized the public health risk remained low and the food supply safe.
Contact Brandon Reid at breid@usatodayco.com.
This article originally appeared on Fond du Lac Reporter: Bird flu safety — avoid sick or dead birds in Northeast Wisconsin
Reporting by Brandon Reid, Fond du Lac Reporter / Fond du Lac Reporter
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