A Maricopa County commercial egg farm has been hit by avian flu affecting more than 2.58 million birds.

The Arizona Department of Agriculture reported that a commercial farm in the county had poultry that tested positive for the virus that was confirmed on Monday through the National Veterinary Services Lab.

While the department did not identify the farm in the press release, the U.S. Department of Agriculture reported the case was listed as active with millions of birds affected.

The case marks the largest report of an avian flu outbreak at a farm or bird site since Feburary as outbreaks around the country had slowed.

Avian flu is fatal in birds and outbreaks in commercial farms, usually spurred by infected wild birds, have had a serious impact on egg production around the U.S. over the past three years, causing egg prices to skyrocket.

According to the Centers for Disease Control and Prevention, 171 million birds have been affected since the outbreak began in January 2022.

The Maricopa County outbreak would be the largest since an Ohio outbreak reported in February that impacted nearly 3.1 million birds.