Bird flu confirmed in Colorado dairy cows as outbreak spreads

The U.S. Department of Agriculture found bird flu in northeast Colorado dairy cows this week, according to state officials.

This is the first time avian flu has been diagnosed in Colorado cattle, the state Department of Agriculture said in its announcement.

Bird flu in dairy cows has been confirmed in eight other states, the USDA said. Those include Idaho, South Dakota, Kansas, New Mexico, Texas, Michigan, Ohio and North Carolina.

On Monday, the Colorado State Veterinarian’s Office was notified of a dairy herd exhibiting symptoms consistent with bird flu. Signs of avian flu in dairy cows include decreased eating, decreased milk production and abnormal colostrum-like milk. Sick cattle appear to recover after supportive care, state officials said.

Samples submitted to the Colorado State University Veterinary Diagnostic Laboratory tested presumptive positive for highly pathogenic avian influenza, or HPAI, on Wednesday and were confirmed by the USDA’s National Veterinary Services Laboratory on Thursday, the state’s news release said.

“We continue to see this ongoing HPAI outbreak evolve and over the last month have seen transmission of the virus now move into dairy cattle,” said Colorado State Veterinarian Maggie Baldwin in a statement. “While we don’t yet completely understand the mechanism of transmission of this virus, we do know that it appears to be spreading from cow to cow and between herds. It is critically important that producers implement enhanced biosecurity measures to mitigate the spread of highly pathogenic avian influenza.”

A Michigan poultry facility and a Texas egg producer have both reported avian flu outbreaks, according to reporting from the Associated Press. Virus developments include infected dairy cows and the first known instance of a human contracting bird flu from a mammal, the AP reported

Colorado’s avian flu response webpage will be updated with the state’s plans for the ongoing outbreak. The state Department of Agriculture is working with the Colorado Department of Public Health and Environment to provide disease control guidance for people exposed in the outbreak, the news release said.

Colorado has 106 dairies and about 200,000 dairy cows.

At this time, there is no concern about the safety of the commercial milk supply because milk is pasteurized before entering the market, according to the USDA and FDA.

Despite health officials saying the risk to the public remains low, people are increasingly concerned in part because the largest producer of fresh eggs in the nation reported an outbreak, the AP reported.

Two human cases of bird flu have been reported in the United States: One in Colorado in 2022 and another in Texas in 2024. Both people had minimal symptoms following exposure to infected animals, the news release said.

“Both dairy and poultry producers should practice enhanced biosecurity and be vigilant about monitoring for and controlling disease in their herds and flocks,” the news release read. “Additional detailed actions can be found in the USDA’s livestock recommendations document, which will be updated as additional information is made available.”