Another case of avian flu has been identified in a person in Colorado, the fourth such case associated with the H5N1 virus that has infected dairy herds in 12 states.

The adult male, an employee at a dairy farm in northeast Colorado who had “direct exposure to dairy cattle infected with avian flu,” reported symptoms of conjunctivitis, or pink eye, the Colorado Department of Public Health and Environment said July 3. 

He has recovered after being given antiviral treatment with oseltamivir “in accordance with CDC guidance,” the agency said.

Specimens sent to the State Public Health Laboratory and the Centers for Disease Control and Prevention tested positive for avian flu, the state health department said.

Other human cases were confirmed in Michigan, where two dairy workers were infected, and in Texas. Separately, in 2022 a poultry worker was infected in Colorado.

Jill Hunsaker Ryan, executive director of the state health department, said its partnership with the Colorado Department of Agriculture “has been crucial in disseminating information to dairy farmers across the state, Coloradans should feel confident that the state is doing everything possible to mitigate the virus.”

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The state pointed to a study released this week by FDA and USDA finding that “the most commonly used pasteurization time and temperature requirements were effective at inactivating the H5N1 HPAI virus in milk. These results complement the FDA’s initial retail sampling study in which all 297 samples of dairy products collected at retail locations were found to be negative for viable H5N1 HPAI virus.”

“The risk to most people remains low,” state epidemiologist Rachel Herlihy said. “Avian flu viruses are currently spreading among animals, but they are not adapted to spread from person to person. Right now, the most important thing to know is that people who have regular exposure to infected animals are at increased risk of infection and should take precautions when they have contact with sick animals.”

The Animal and Plant Health Inspection Service says 139 herds in 12 states have been infected since the first herd was identified in Texas in March.

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