Mexico Death Tied to Bird Flu Strain Never Before Seen in People

A man in Mexico died after contracting a strain of bird flu that hasn’t been confirmed in humans before, the World Health Organization said Wednesday. 

The virus was detected in a 59-year-old patient who had been hospitalized in Mexico City. The man died one week after developing a fever, shortness of breath and diarrhea. It’s the first lab-confirmed case of a person contracting a form of bird flu known as H5N2, the WHO said in a statement, raising questions about a strain that has largely been under the radar. The current bird flu outbreak in US dairy cows is being driven by a different strain — H5N1. 

The patient, who lived in central Mexico, had no history of exposure to poultry or other animals. The Mexican government doesn’t know where he was exposed to the virus, though the strain of avian influenza has been reported in poultry in the Mexican state where the person lived. 

The current risk posed by the H5N2 virus to the general public is low, according to the WHO, which said no further cases were reported after an investigation.

The H5N2-infected man had several underlying health conditions, including chronic kidney disease, type 2 diabetes and longstanding hypertension, according to Mexico’s health ministry Wednesday. He had been bedridden for three weeks prior to the onset of acute symptoms in mid-April, the WHO added, citing the patient’s relatives. Though hospitalized on April 24, the man died the same day. 

Mexican authorities reported the fatal case to the WHO on May 23 after confirming the presence of the virus in a sample from the deceased man.

While the man in Central Mexico marks the first laboratory-confirmed case of H5N2 in humans, researchers have identified people with antibodies that could signal prior infections.

Katrine Wallace, an epidemiologist with the University of Illinois Chicago School of Public Health, said that H5N2 poses a low risk to public health because it hasn’t shown an ability to be transmitted between humans. To that end, it’s concerning that the patient isn’t known to have had exposure to animals which are the most likely source of disease, she added. 

Wallace said more surveillance is needed to fill in the gaps of information. 

“It’s so crazy that we don’t know where this is coming from,” she said.

The Mexican government has begun monitoring wild birds for H5N2 in the wetlands of Tlahuac in Mexico City, as well as farms, backyards and other areas near where the man resided. So far, no infected birds have been identified, the health ministry said in Wednesday’s statement. 

The US Centers for Disease Control and Prevention didn’t immediately respond to requests for comment. 

In the US, the H5N1 outbreak in cattle continues to expand its geographic reach. On Wednesday, Iowa announced it had identified infected cows, bringing the total number of states that have detected bird flu in herds to 10. So far this year, three US-based farmworkers have tested positive for bird flu — one in Texas and two in Michigan. They had symptoms of eye irritation and one had a cough. There have been no fatal human cases associated with the US H5N1 outbreak.