Federal and state investigators in Colorado are investigating an outbreak of the highly pathogenic H5N1 avian influenza virus at a commercial poultry farm, which has resulted in four confirmed human cases and one suspected case among poultry workers.
The U.S. Centers for Disease Control and Prevention (CDC) has deployed a nine-member field team to support Colorado’s assessment of the outbreak and the human cases. The CDC stated that the risk to the general public remains low, but noted that could change as the situation is monitored.
The poultry workers were involved in culling chickens at the affected egg facility in northeast Colorado. All the infected workers reported mild illness, including conjunctivitis, eye tearing, fever, chills, coughing, and sore throat/runny nose.
This is the first reported incident of H5N1 bird flu infecting poultry workers in the United States since 2022. It follows a recent outbreak of the virus in U.S. dairy cattle that has infected an additional four farm workers since March.
Experts say the cases among poultry workers are somewhat less concerning than the dairy cow outbreak, as the poultry cases appear to be a result of direct avian-to-human transmission, which is a more common route of infection. However, they still emphasize the importance of proper personal protective equipment for workers involved in depopulating infected flocks.
Genetic sequencing of the virus is underway to look for any mutations that could signal the virus is adapting to humans. Additional cases may be reported as monitoring and testing continues.