The U.S. Centers for Disease Control and Prevention (CDC) that four workers responding to an H5N1 avian influenza outbreak in Colorado have confirmed cases of highly pathogenic avian influenza (HPAI) while a fifth worker is a presumed-positive case.
According to a press release from the Colorado Department of Public Health and Environment (CDPHE), the workers were culling poultry at a commercial laying hen operation in the state and exhibited mild symptoms, including conjunctivitis and common respiratory infection symptoms. However, none of the patients required hospitalization.
State epidemiologists believe the poultry workers’ cases are a result of working directly with infected poultry.
According to CDPHE, three of the confirmed human cases are from samples that the State Public Health Laboratory sent to CDC on July 12 for confirmatory testing. The fourth case was an additional presumptive detected by the state lab later that evening that was since confirmed by the CDC.
Samples from a fifth worker were presumed positive at the state lab on July 13 and will be sent to CDC for confirmation.
No additional test results are pending at this time.
CDPHE did not identify the farm where they were working, or the exact location, other than stating it was in northeast Colorado. Information from the United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) shows that the last confirmed instance of HPAI in a commercial layer operation was confirmed in Weld County on July 8.
No other layer operations in the state have been affected by HPAI in 2024.
These latest confirmed cases have doubled the number of H5N1 cases in humans in the United States in 2024, with the other cases being confirmed in people who were working with dairy cattle that had been infected by H5N1. One other case had been confirmed in Colorado, one was in Texas and two were in Pennsylvania.
View our continuing coverage of the global avian influenza situation.
