WASHINGTON — Public health officials have diagnosed a Colorado farm worker with the country’s fourth human case of highly pathogenic avian influenza, the Centers for Disease Control and Prevention and the state’s department of health reported Wednesday.

The Colorado case, the state’s first this year related to spread from dairy cattle to humans, was reported after an adult man working on a farm in the northeast region of the state experienced conjunctivitis or pink eye.

The unidentified man, who has since recovered, was being monitored by public health officials after dairy cattle on the farm he worked on tested positive for H5N1, or bird flu.

Dr. Rachel Herlihy, an epidemiologist with the Colorado Department of Public Health and Environment, wrote in a statement announcing the diagnosis that the “risk to most people remains low.”

“Avian flu viruses are currently spreading among animals, but they are not adapted to spread from person to person,” Herlihy wrote in the statement. “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.”

Nationwide, the U.S. Department of Agriculture has reported bird flu in 139 dairy herds throughout a dozen states, including Colorado, Idaho, Iowa, Kansas, Michigan, Minnesota, New Mexico, North Carolina, Ohio, South Dakota, Texas and Wyoming.

In Colorado, there have been 27 dairy herds where at least one cow has tested positive for H5N1 since the outbreak began, according to data from the USDA.

The other three human cases reported this year include two dairy farm workers in Michigan and one in Texas. Two of the cases were pink eye, while one of the Michigan patients experienced mild respiratory symptoms.

The Colorado Department of Public Health and Environment wrote in its announcement Wednesday that 2022 was the last time a person within the state was diagnosed with bird flu. That time it was the result of infected poultry.

Bird flu continues to spread in the country’s poultry flocks as well, though that industry has had much more time to adjust and get its workers used to wearing personal protective equipment than dairy farmers have.

More than 97 million poultry throughout 48 states have tested positive for H5N1 since this outbreak began in January 2022, according to reports from the Centers for Disease Control and Prevention.

Unlike dairy cows, which generally recover from bird flu, poultry flocks are culled after a diagnosis, making response and recovery to H5N1 vastly different.

The USDA began a voluntary pilot program for dairy farmers in late June that gives them the option to have their herd’s bulk milk tanks tested. The program is designed to make it easier for farmers to transport their cows across state lines.

The U.S. Department of Health and Human Services announced Tuesday that it would direct $176 million to Moderna to develop a vaccine that would inoculate people against the virus.