1st fatal human case of bird flu subtype confirmed in Mexico: WHO

The World Health Organization confirmed on Wednesday the first-ever fatal case of a subtype of bird flu in Mexico.

It is the first laboratory-confirmed human case of the H5N2 strain of bird flu, or avian influenza, reported globally and the first-ever reported case in Mexico.

This strain is different than the bird flu strain that is currently circulating in livestock in the United States and has infected three dairy workers in the U.S.

The Mexico patient was a 59-year-old resident with no history of exposure to poultry or other animals, according to the WHO.

On April 17, the patient developed fever, nausea, diarrhea, shortness of breath and general malaise. They were hospitalized on April 24 at the National Institute of Respiratory Diseases in Mexico City and died the same day.

The patient's relatives said the person had underlying conditions and they had been bedridden for three weeks for other reasons prior to contracting bird flu, the WHO said. On Wednesday night, Mexico's Health Ministry said the patient had "a history of chronic kidney disease, type 2 diabetes [and] long-term systemic arterial hypertension."

Test results eventually revealed the patient was infected with bird flu subtype H5N2, which has never been documented in humans before.

No further cases have been documented during health officials' investigation, according to the WHO. Of the 17 people the patient came into contact with at the hospital, one person reported a runny nose in late April. Samples taken from the contacts tested negative for flu and COVID-19.

Twelve additional people the patient came into contact with -- seven with symptoms and five without -- were identified near the patient's residence. Nasal samples, throat samples and blood samples were taken from the contacts. The nose and throat samples tested negative for COVID-19 and results from the blood samples are ongoing.

Mexico's Ministry of Health said in a statement Wednesday that "all samples from identified contacts have been negative" for H5N2.

The WHO said while a human infection with bird flu "has the potential for high public health impact," the global health agency said the current risk to the general population is low.

Mexico's Ministry of Health echoed the WHO in its statement.

"The Ministry of Health informs that there is no risk of contagion for the population with the detection of the first human case of low pathogenic avian influenza A (H5N2) in Mexico, since there is no identified source of infection," the statement read.

On Thursday, Mexican Health Secretary Jorge Alcocer said there is no evidence of human-to-human transmission and reiterated that the patient had pre-existing health issues, including diabetes and kidney problems.

"There is no reason to avoid eating chicken and its products or to be worried about it," Alcocer said in public remarks.

In the U.S., an outbreak of the H5N1 strain has been found to sicken millions of birds as well as older dairy cows. So far, three farmworkers have been sickened in the U.S., one in Texas and two in Michigan.

All three had mild symptoms and have recovered or are recovering. There is no evidence of human-to-human transmission and the risk to the general public is low, according to the Centers for Disease Control and Prevention (CDC).

"While both H5N2 and H5N1 belong to the same family of influenza A viruses, H5N1 has been known to infect humans for years, whereas this is the first-ever reported case of H5N2 in humans," said Dr. John Brownstein, an epidemiologist and chief innovation office at Boston Children's Hospital and an ABC News contributor. "The good news is that neither H5N2 nor H5N1 have demonstrated human-to-human transmission so far. However, this first case is a wake-up call. It reminds us that influenza viruses can evolve, and continued surveillance of these viruses in both animals and humans is crucial."