CDC Report Details Avian Influenza Among Colorado Agricultural Workers

In July, nine workers at two Colorado poultry facilities tested positive for the A(H5N1) virus that causes highly pathogenic avian influenza (HPAI), according to a report published today by CDC. This cluster of occupational, poultry exposure-associated human cases is the first reported in the United States. The workers had conjunctivitis and experienced mild illness, including fevers and sore throats.

The workers were among more than 660 contracted to conduct euthanasia and carcass removal and disposal in response to the confirmation of HPAI A(H5N1) among poultry at the facilities. Two days after the euthanasia work began, the Colorado Department of Public Health and Environment (CDPHE) was notified that several workers were feeling ill. CDPHE delivered goggles, N95 filtering facepiece respirators, and nitrile gloves to one of the facilities where it was reported that PPE compliance was low.

According to the report, the facilities where the exposures occurred were cage free, which required workers to physically catch birds. This activity increased the likelihood that PPE would be displaced or damaged. Other challenges included delivering training to a predominantly Spanish-speaking worker population who had been hired quickly to address what was considered an urgent problem.

Prior to this outbreak, there had been five cases of influenza A(H5) reported in the U.S., all of which were in Colorado. The first, in 2022, was associated with poultry exposure. The other four cases occurred among dairy workers from April through July 2024.

“These findings suggest that poultry workers who are exposed to enclosed environments with birds infected with HPAI A(H5N1) virus are at increased risk for infection,” the report concludes. “Given the continued circulation of this virus in the United States, public health agencies should proactively prepare for additional human cases in both dairy and poultry facilities.”

More information is available from today’s issue of CDC’s Morbidity and Mortality Weekly Report.