Public health officials in Colorado announced on Wednesday that a man had tested positive for avian flu after reporting mild symptoms, including conjunctivitis, or pink eye.
Officials said that the man, a dairy farm employee, recovered from his exposure to infected cattle after receiving antiviral treatment.
Since the confirmation of avian flu in cows in March, the US has reported four human cases of bird flu. The first three people to test positive were also dairy farm workers who recovered.
The first two workers to contract the virus had mild pink eyes. In the third case, the worker had mild respiratory symptoms.
In a statement, the Centres for Disease Control and Prevention confirmed the case and said the risk to the general public from bird flu remains low, although people with exposure to infected animals are at greater risk.
The virus has infected cows at 139 farms in 12 US states, according to the U.S. Department of Agriculture. 27 of those outbreaks occurred in Colorado.
On Tuesday, Moderna signed a $176 million government contract to advance the development of its human bird flu vaccine.
The USDA is conducting its own research and soliciting information from about two dozen companies on a potential bird flu vaccine for cattle, but the agency has stated that it hopes to eliminate the virus from dairy herds without using a vaccine.
