Nearly 1 million chickens were killed at an Illinois farm after a bird flu outbreak became the nation’s largest active outbreak this week.

The outbreak affected 934,600 birds at a commercial table egg layer facility in Clinton County, Illinois, the United States Department of Agriculture confirmed . It reportedly occurred at Rose Acre Farms, located outside Germantown, village officials told KSDK .

Rose Acre Farms is the second-largest egg producer in the U.S., according to the company's website . With no treatment available for highly pathogenic avian influenza , better known as bird flu, authorities must kill infected and exposed birds to contain the virus.

Losing nearly a million hens could disrupt egg production and put further pressure on prices as supplies tighten.

The scale of the Illinois outbreak far exceeds other active cases nationwide.…