Avian influenza outbreak largest animal disease outbreak ever in U.S.

The avian influenza (HPAI) outbreak that began in February 2022 is now the nation’s largest animal disease event ever, according to the U.S. Department of Agriculture (USDA). It has spread from poultry to cattle and has infected humans. The disease has spread to nearly every state.

The USDA reported that 97.26 million birds in commercial and backyard flocks, as well as 137 dairy cattle herds, have been affected since the outbreak began. In a June 2024 technical report, the CDC reported the virus has also infected three farm workers in Texas and Michigan this year.

Since December 2023, the number of states where HPAI has been detected has risen from 27 to 48. Since May 24, 2024, 6.41 million birds have been affected, according to the USDA.

Brook Duer, staff attorney at Penn State Center for Agricultural and Shale Law, said HPAI remains as transmissible as it was when it was first detected in 2015.

“We are in uncharted territory with HPAI in poultry – it is by far the largest animal disease event in U.S. history,” Duer said. “HPAI may already be a permanent backdrop to poultry and egg production.”

The foundational statutes, regulations, manuals and procedures that give USDA its authority will be examined through the lens of HPAI outbreaks in poultry and cattle during the National Agricultural Law Center’s next webinar, “HPAI in Poultry and Cattle: How Can We Miss You If You Won’t Go Away?” The webinar will be presented by Duer.

The spillover to dairy cattle has brought more insights and questions. Each host species’ unique response to the virus is vastly different and the virus can mutate quickly, Duer said.

“With dairy cattle, the disease can go nearly undetected through traditional observation of symptoms. This allows it to reach a point in the food production supply chain where pasteurization becomes the primary tool. That might be seen as uncomfortably close to the consumer,” Duer said. “Understanding how USDA-APHIS’ response has progressed to date, and why, will allow producers to better anticipate what research still needs to be done to get the answers producers want.”

The webinar will be held Wednesday (July 17).

A death in Mexico that was initially linked to HPAI has since been reinvestigated and attributed to other causes, according to the World Health Organization.