Four Colorado poultry workers diagnosed with bird flu

Health officials have confirmed that four poultry farmers in Colorado have been diagnosed with bird flu.

The new cases bring the U.S. total to nine since the first human case in the current outbreak was discovered in 2022, also in a poultry worker in Colorado. Eight of the nine were reported this year.

Their illnesses were relatively mild — red and irritated eyes and common respiratory symptoms such as fever, chills, cough, sore throat and runny nose. None required hospitalization, officials said.

The other cases in the US were also mild.

A fifth person with symptoms is being tested, but those results are not yet available, officials said. The workers were culling poultry at a farm in northeastern Colorado, state health officials said. All had direct contact with infected birds.

Since 2020, an avian flu virus has been spreading among mammals, including dogs, cats, skunks, bears, and even seals and porpoises, in dozens of countries. Earlier this year, the virus, known as H5N1, was found in U.S. cattle and is now circulating in livestock in several states.

Health officials continue to characterize the threat to the general public as low and the virus has not spread between people. But officials are keeping a close eye on it because previous versions of the same virus have been deadly to humans.

The Centers for Disease Control and Prevention has sent a nine-person team to Colorado at the state’s request to assist with the investigation, CDC officials said.

Earlier this year, similar cases occurred among dairy farm workers in Michigan, Texas and Colorado.

The virus found in the latest four cases is at least partially identical to the type found in the earlier cases in the U.S., but further genetic testing is being done to make sure it is exactly the same, officials said.

According to the U.S. Department of Agriculture, the H5N1 virus has been confirmed in 152 dairy herds in 12 states since Friday. Hundreds of commercial poultry herds in more than 30 states have reported H5N1 or other forms of bird flu.