5 human cases of bird flu in Colorado poultry workers, health officials report ( www.cbsnews.com )

Five poultry workers from a farm in northeast Colorado have bird flu, state and federal health officials reported Sunday. Four of the cases have been confirmed by the U.S. Centers for Disease Control and Prevention, and one is presumptively positive for H5N1, also known as avian influenza, and is pending confirmation.

The disease was contracted while working at a "commercial egg layer operation," the Colorado Department of Public Health and Environment said in a statement Sunday.

On Friday, when only three cases were confirmed, the CDC said they worked "at a poultry facility experiencing an outbreak of the H5N1 virus that is circulating in wild birds and has been causing multistate outbreaks in dairy cows and poultry."