Testing has confirmed four poultry workers in Colorado were infected with the H5N1 bird flu virus, state health officials said Sunday, with results of a fifth presumptive positive case still pending. The U.S. Centers for Disease Control and Prevention confirmed the infections, which the agency has said could trigger a pandemic should the virus mutate and become easily transmissible between people, Reuters reported. According to the Colorado Department of Public Health and Environment, the infected workers were culling poultry at a farm in the northeast region of the state “and exhibited mild symptoms, including conjunctivitis (pink eye) and common respiratory infection symptoms.” None of the workers were hospitalized and state epidemiologists “suspect the poultry workers’ cases are a result of working directly with infected poultry,” officials said. It remains safe to eat properly handled and cooked poultry products, the department said.