The Colorado Department of Public Health and Environment announced Sunday that a total of five human cases have been reported among workers responding to an avian influenza outbreak at a commercial egg farm. Four cases have been confirmed, with the fifth “preliminary positive and pending confirmation by CDC.” There have been four confirmed cases of human infection after contact with dairy cows, and one case of infection in poultry in 2022.
The workers had “mild symptoms” and none were hospitalized, according to the statement, specifically conjunctivitis and “symptoms of a common respiratory infection.” Public health officials believe the workers contracted the virus through direct work with infected poultry. The CDC said Friday that the risk to the public remains low. “There are no indications of an unexpected increase in influenza activity in Colorado or other states with H5 avian influenza outbreaks in cattle or poultry,” the agency said.
This latest development is part of a months-long story. In late March, a worker at a commercial dairy farm in Texas developed conjunctivitis. He eventually tested positive for highly pathogenic avian influenza type A H5N1, also known as bird flu. Scientists were shocked to find that the host was not birds but cattle, and that large amounts of H5N1 were found in infected cattle. As Salon previously reported, experts have since expressed concern that more cases are going undetected than are reported.
Notably, the Colorado worker appears to have contracted the virus from poultry rather than cattle, and this news comes amid reports that bird flu is mutating in a way that makes it more infectious to humans.