The Wisconsin Department of Agriculture, Trade, and Consumer Protection confirms a case of highly pathogenic avian influenza in a backyard chicken flock in Rock County. Samples from the flock are tested, and the National Veterinary Services Laboratories confirm the findings Saturday.  Birds on the property have been depopulated to prevent the spread of the disease.  The state ag agency and the U.S. Department of Agriculture are working closely with animal health officials on a joint response.  The virus recently hit a poultry farm in Jefferson County, which led to the destroying of close to three million chickens.  Officials say the disease does not present an immediate public health concern and does not pose a food safety risk.