Three poultry workers in northeast Colorado are presumed to have fallen ill with bird flu as more human cases sprout across the U.S., state and federal health officials said Friday. The three workers were working to depopulate chickens at an egg-laying facility experiencing an outbreak of H5N1 avian influenza, which has been circulating in wild birds and has caused multi-state outbreaks in dairy cows, the Centers for Disease Control and Prevention said. Colorado epidemiologists suspected the poultry workers’ infections to be a result of working directly with infected poultry, the state Department of Public Health and Environment said.

The workers have exhibited mild symptoms that include conjunctivitis, or pink eye, and common respiratory infection symptoms, state officials said. None of the workers were hospitalized. Read more