U.S. health officials on Friday confirmed two additional human cases of bird flu linked to a large outbreak at a Colorado poultry farm.
Earlier last week, the Centers for Disease Control and Prevention confirmed four other cases following an avian influenza outbreak at a Weld County egg farm. Workers were exposed to the virus in the process of killing 1.8 million birds to contain further spread. Colorado state officials also have identified a presumptive positive case in a worker at a separate egg farm over the weekend.
The cases in Colorado widen an outbreak among commercial birds and dairy cattle, which epidemiologists have been carefully monitoring for potential spillover into humans. Since April, 10 human cases of H5N1 have been confirmed in the U.S, with four linked to infected dairy cattle.
Still, despite a growing number of human cases, risk of bird flu spreading to the general public remains low, and there is still no evidence of human-to-human transmission. A study of Michigan farm workers exposed to infected dairy cattle also found no evidence of asymptomatic cases, which would have indicated the outbreak is larger than what has been reported.
The six infected workers in Colorado experienced mild eye and respiratory symptoms, according to a health advisory from the CDC, and workers exposed to the virus have received antiviral medications.
Extreme temperatures made it more difficult for workers to wear protective gear, which could have contributed to the spread of the virus. Workers' goggles and N95 masks apparently slipped amid 104 degree temperatures while industrial fans blew feathers and other infected materials into the air, said Dr. Nirav Shah, principal deputy director of the CDC, according to the Washington Post.
Colorado has been hit hard by the virus as most of its dairy production is concentrated within northern Weld County. The state is looking to conduct more sample testing to monitor and respond to the virus more effectively.
Over the past month, 3.1 million chickens at two egg farms and 28 dairy herds across Colorado have been affected by bird flu, according to the U.S. Department of Agriculture. The second poultry outbreak occurred at another egg farm in Weld County, affecting 1.3 million birds.
As the virus spreads, state and federal epidemiologists are looking for genetic variations and potential changes in transmission patterns. A field team of 10 people from the CDC has been deployed to support Colorado’s response to the ongoing outbreak in the form of daily visits, treatments, testings and follow-up visits.
