Forty commercial poultry flocks in Mercer County, Ohio, have now been affected by highly pathogenic avian influenza (HPAI).
The United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) reported that the presence of HPAI was confirmed in a flock of 125,800 commercial laying hens in Mercer County on February 13.
Prior to 2025, Mercer County had been free of HPAI during the 2022-25 outbreak, until the county had its first confirmed case on January 14. Since that time, 40 commercial flocks have been affected by the virus, involving commercial meat turkeys, commercial layers, commercial layer pullets and commercial ducks.
Mercer County is also the site of the state’s first probable human infection of avian influenza. The Ohio Department of Health identified that patient as a farm worker who had been exposed to infected poultry.
APHIS also reported that on February 13, the presence of HPAI was confirmed in a commercial flock of 210,600 commercial laying hens in Auglaize County. This is the second commercial flock in that county to be struck by the virus in 2025, with the other being a commercial meat turkey flock. Like Mercer County, Auglaize County had been spared by HPAI until 2025.
These two incidences bring the total number of commercial Ohio flocks to be struck by HPAI to 60.
Elsewhere in Ohio, Darke County has had 17 commercial flocks affected by HPAI in 2025, and Van Wert County has had one.
Darke, Van Wert and Auglaize counties all border Mercer County, as do Jay and Adams counties in Indiana. Jay County has had four confirmed flock infections in 2025, and Adams County has had one.
View our continuing coverage of the global avian influenza situation.
To learn more about HPAI cases in commercial poultry flocks in the United States, Mexico and Canada, see an interactive map on WATTPoultry.com.
