The US has confirmed the first known human case of H5 bird flu in a person in the state of Colorado, the Centers for Disease Control and Prevention (CDC) announced.

The person tested positive for the avian influenza A (H5) virus and was involved in the culling of poultry presumed to have had H5N1 bird flu, Xinhua news agency quoted the CDC as saying on Thursday.

The patient reported fatigue for a few days as the only symptom and has since recovered.

According to the CDC, the patient is being isolated and treated with the influenza antiviral drug oseltamivir.

"This case does not change the human risk assessment for the general public, which CDC considers to be low," the health agency said.

CDC has been monitoring for illness among people exposed to H5N1 virus-infected birds since these outbreaks were detected in wild birds and poultry since late 2021.

To date, H5N1 viruses have been found in commercial and backyard birds in 29 states and in wild birds in 34 states, according to the CDC.

The agency has tracked the health of more than 2,500 people with exposure to H5N1 virus-infected birds and this is the only human case that has been found to date.

It is the second human case worldwide associated with this specific group of H5 viruses that are currently predominant.

The first case was reported in Britain in December 2021.