Public health officials in Colorado on Wednesday announced an adult man had tested positive for avian flu after reporting mild symptoms, including conjunctivitis, or pink eye.

The man is an employee at a dairy farm who had exposure to infected cattle and recovered after antiviral treatment, officials said.

The case is the fourth human case of bird flu reported in the U.S. since avian flu began spreading among dairy herds in early March. The other three people to test positive were also dairy farm workers who recovered after experiencing mild pink eye and respiratory symptoms.

Federal public health officials have said the risk to the general public from bird flu is low. The virus has infected cows at 139 farms in 12 states.