WELD COUNTY, Colo. — A massive culling operation at an egg-laying facility in Weld County earlier this month did not lead to new cases of highly pathogenic avian influenza among Colorado poultry workers, state health officials said Tuesday.
The announcement from the Colorado Department of Public Health and Environment (CDPHE) comes after state health officials said they had concluded a “coordinated response” involving more than 100 people following confirmation by the USDA of highly pathogenic avian influenza (HPAI) at the Weld County egg-laying facility in late January.
The state response, which included the CDPHE, the Colorado Department of Agriculture (CDA), the State Emergency Operation Center (SEOC), and Weld County, began after the producer notified the CDA that they suspected the virus — more commonly known as bird flu — was circulating at the facility following the discovery of dead poultry at the site.
Preliminary confirmation at the state level prompted the CDA to stop all movement of the facility’s 1.3 million chickens and allowed Lt. Governor Dianne Primavera to declare a disaster for the county, freeing up emergency funds to prevent the further spread of the virus into other farms and potentially more poultry workers.
Weld County
Bird flu outbreak in Weld County chicken facility prompts disaster declaration
As part of the response to Colorado's first outbreak at a commercial egg-laying facility since the summer of 2024, Dr. Rachel Herlihy, the state epidemiologist and CDPHE's deputy chief medical officer, said her agency prioritized early health monitoring "based on lessons learned from prior responses."
Though it was not immediately clear what that response looked like when Colorado detected bird flu among 9 poultry workers in a span of two weeks in 2024, CDPHE officials said during this response, they tested four workers who developed mild symptoms between one and four days after working at the depopulation site "as part of precautionary monitoring." None tested positive for H5N1 bird flu.
The response by the state health department also included psychological first aid and mental health resources as “poultry depopulation operations can be physically and emotionally demanding,” Herlihy said.
While transmission of H5N1 from birds to people is very rare, it does happen, but this usually requires close and prolonged contact with infected birds. People who come into contact with sick poultry or cattle are at greater risk of becoming infected with the virus, according to the CDPHE.
Even though the risk to the general public is low, health officials advise people to avoid touching sick or dead birds to reduce their chances of becoming infected with bird flu, which has historically killed about half of the people it infects, according to the World Health Organization. Current U.S. estimates, however, suggest newer versions of the virus have about a 3% mortality rate.
Though depopulation and disposal operations at the egg-laying facility wrapped up Friday, the CDA is still working with the producer on eliminating the virus from the premises and the facility remains under quarantine.
State health officials advised people — especially those who work with poultry or dairy cattle and who develops flu-like symptoms — to seek medical care or call CDPHE at 303-692-2700 (or 303-370-9395 after normal business hours), so the state health department can facilitate flu testing and provide antiviral medication if needed.
This most recent outbreak in Weld County is the fourth across the state so far this year, according to the CDA. In all, 10 Colorado workers have tested positive for the virus since 2022.
Nationwide, 71 people have tested positive for bird flu since the unprecedented spillover of the virus into dairy cattle in 2024, according to the U.S. Centers for Disease Control and Prevention (CDC). Of those, two people have died.
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