In a press statement released on Wednesday, June 5, the WHO stated there was no need for panic, as the risk of the disease remains low in humans.
Detailing the background of the victim, the WHO statement reported that the 59-year-old man died in Mexico City in April. He is said to have developed symptoms including fever, shortness of breath, diarrhoea, and nausea. The WHO added that it is carefully monitoring the situation and was relieved that none of the deceased's immediate family members had contracted the disease.
Initial tests showed an unidentified type of flu, which subsequent weeks of lab testing confirmed as A(H5N2), the WHO said.
It was the "first laboratory-confirmed human case of infection with an influenza A(H5N2) virus reported globally," the agency added.
It is unclear how he contracted it, although there have been cases in some poultry farms in Mexico.
Infections like this can sometimes pass from animals to humans.
The man had other underlying health issues that likely made him more vulnerable.
He had been bedridden for weeks before becoming ill with fever and shortness of breath from bird flu, according to officials.
There is no evidence that the virus could start spreading between people and cause an outbreak, they say.