Stat Public health experts who’ve been following the surprising spillover of H5N1 bird flu into America’s dairy cattle herds now have all eyes on Colorado, waiting to see if a cluster of human cases there might balloon into something bigger. On July 14, Colorado officials announced that five workers involved in the culling of 1.8 million chickens at a large H5N1-infected egg farm in Weld County had tested positive for the virus. And the strain infecting the workers appears to be closely related to the virus infecting cows in Colorado and at least 12 other states.
On Friday, the Centers for Disease Control and Prevention confirmed a sixth case among the Colorado poultry workers. Almost 70 individuals involved in the “depopulation” operation were tested for H5N1 after showing symptoms of the disease, according to a spokesperson for the Colorado Department of Public Health and the Environment. On Saturday, the state announced it had found a possible seventh human case; the CDC, which must conduct confirmatory testing, is expected to receive the sample on Tuesday.
The six Colorado cases were all mild, with some experiencing the more traditional flu signs of fever and cough, and others having conjunctivitis, a symptom that’s been seen with some of the dairy workers who’ve been infected during the outbreak. But it’s the first time multiple human cases have been reported on a single farm in the U.S., raising questions about whether the virus has changed or the environmental factors presented unique opportunities for it to spread.