Bird flu confirmed in rats for first time, USDA reports

Bird flu has been detected in rats for the first time, the U.S. Department of Agriculture's Animal and Plant Health Inspection Service confirmed Wednesday. 

Four black rats were confirmed to have H5N1 avian flu in late January in Riverside County, California, where two recent poultry outbreaks were reported, the agency said. 

Officials have previously confirmed the virus in mice found on affected farms.