U.S. health officials confirm four new cases of bird flu among Colorado poultry workers

Four Colorado poultry workers have been diagnosed with bird flu, health officials confirmed Sunday.

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

Their symptoms were relatively mild: red, irritated eyes and common symptoms of respiratory infections such as fever, chills, cough, sore throat and runny nose. No cases have been hospitalized, authorities said. The other cases in the United States are also mild.

A fifth person with symptoms is being tested, but the results are not yet available, authorities said. The workers were slaughtering poultry at a farm in northeastern Colorado, according to state health officials. 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 many countries. Earlier this year, the virus, known as H5N1, was detected in U.S. livestock and is now circulating in livestock in several states.

Health officials continue to consider the threat to the general population to be low and that the virus has not spread from person to person. But officials remain very vigilant because previous versions of the same virus have been deadly to humans.

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

These cases were reported earlier this year among dairy farm workers in Michigan, Texas and Colorado.

The virus detected in the latest four cases is at least partly identical to the type found in previous U.S. cases, but further genetic analysis is underway to ensure it is exactly the same, officials said.

According to the U.S. Department of Agriculture, H5N1 was confirmed Friday on 152 dairy farms in 12 states. Hundreds of commercial poultry farms in more than 30 states have reported H5N1 or other types of bird flu.