DENVER (KDVR) — Bird flu killed most of a backyard chicken flock in Colorado, a federal lab confirmed, as officials warned of a rise in the disease during migratory season.

The new case of highly pathogenic avian influenza was confirmed in Weld County after 20 of the flock’s 24 chickens died, according to the Colorado Department of Agriculture. The rest of the chickens were euthanized.

The chickens were exposed to sick and dying wild geese.

“Unfortunately, as we see the fall movement of migratory birds through the United States, including Colorado, we are beginning to see HPAI cases increase again,” Colorado State Veterinarian Dr. Maggie Baldwin said in a statement.

The disease was confirmed by the U.S. Department of Agriculture’s National Veterinary Services Laboratory.

“We will continue to work with commercial poultry and egg producers as well as backyard flock owners to ensure they adhere to strict biosecurity practices that can help keep birds safe and decrease the spread of the virus,” Baldwin said.

There had been a break from cases over the spring and summer. State records show the last confirmed bird flu cases in Colorado were in late May in Moffat and Routt counties.

Colorado has been suffering the largest foreign animal disease outbreak in the state’s history, the ag department said in the release. Since April 2022, more than 6.2 million domestic poultry have been lost to the disease.

Stay aware of signs of bird flu

All poultry owners are warned to protect their birds from the disease, and everyone is urged to stay vigilant around avian wildlife.

Domestic bird owners should take extra precautions, like:

  • preventing interaction between domestic and wild birds,
  • keeping food and water sources away from migrating birds, 
  • and monitoring flocks for signs of illness or death. 

If you have sick birds or birds that have died from unknown causes, help is available through the Colorado Avian Health Call Line at Colorado State University: 970-297-4008.

If you find three or more dead wild birds in a specific area within a two-week period, or if you see live birds showing clinical signs of disease, you are urged to contact your local Colorado Parks and Wildlife office.