NEW YORK — The mysterious death of a man in Mexico who had a type of bird flu it is not linked to outbreaks of a different kind on U.S. dairy farms, experts say.
Here’s a look at the case and different types of bird flu.
A 59-year-old man in Mexico who was bedridden due to chronic health problems developed a fever, shortness of breath and diarrhea in April. He died a week laterand the World Health Organization reported this this week.
The WHO said it was the first time this version of bird flu – H5N2 – had been seen in a person.
A different version of bird flu – H5N1 – has been infecting flocks of birds in recent years, leading to the culling of millions of birds. It has also spread among all different types of animals around the world.
This year, that flu was detected on US dairy farms. Dozens of herds have had infections, most recently in Iowa It is Minnesota.
The cow outbreak is linked to three reported illnesses in farmworkers, one in Texas and two in Michigan. Each had only mild symptoms.
So-called influenza A viruses are the only viruses linked to human flu pandemics, so their appearance in animals and people is a concern. These viruses are divided into subtypes based on the types of proteins they have on their surface – hemagglutinin (H) and neuraminidase (N).
Scientists say there are 18 different “H” subtypes and 11 different “N” subtypes, and they appear in countless combinations. H1N1 and H3N2 are common causes of seasonal flu among humans. There are many versions seen in animals as well.
H5N1, the version that has worried some North American scientists lately, has historically been seen mainly in birds, but in recent years it has spread to a wide variety of mammals.
H5N2 has long been seen in Mexican poultry and farms vaccinate against it.
It is also no stranger to the United States. An outbreak of H5N2 struck a flock of 7,000 chickens in south-central Texas in 2004, the first time in two decades that an avian flu dangerous to birds appeared in the United States.
H5N2 was also primarily responsible for a wave of outbreaks on commercial poultry farms in the US in 2014 and 2015.
Over the years, H5N2 has fluctuated between being considered a mild threat to birds and a serious threat, but has not been considered a major threat to humans.
A decade ago, researchers used mice and ferrets to study the strain that was afflicting U.S. poultry at the time and concluded that it was less likely to spread and less lethal than H5N1. Authorities also said there was no evidence it was spreading among people.
Rare cases of animal infections are reported every year, so it is not unexpected that a person has been diagnosed with H5N2.
“If you’re a glass-half-full kind of person, you’d say, ‘This is the system doing exactly what it’s supposed to do: detect and document these rare human infections, where years ago we were stumbling in the dark.’ ” said Matthew Ferrari, director of the Center for Infectious Disease Dynamics at Penn State.
In fact, Mexico’s Health Secretary Jorge Alcocer said that kidney and respiratory failure – not the virus – caused the man’s death.
Some experts said it’s worth noting that it’s not known how he caught the man who caught H5N2.
“The fact that there was no reported contact (with an infected bird) raises the possibility that it was infected by someone else who visited it, but it is premature to draw those conclusions,” said Richard Webby, a flu researcher at St. of Children’s Research in Memphis.
At this point, H5N2 is still considered a minor threat compared to some of the other types of bird flu out there. Most human illnesses have been attributed to the H7N9, H5N6, and H5N1 avian influenza viruses.
From early 2013 until October 2017, five outbreaks of H7N9 were blamed for the deaths of more than 600 people in China. And at least 18 people have died in China during an H5N6 outbreak in 2021, according to the U.S. Centers for Disease Control and Prevention.
H5N1 was first identified in 1959, but it didn’t really start to worry health authorities until an outbreak in Hong Kong in 1997 that involved serious human illness and death.
H5N1 cases have continued since then, the vast majority of them involving direct contact between infected people and animals. Globally, more than 460 human deaths have been identified since 2003, according to WHO statistics that suggest the disease can kill up to half of those declared infected.
Like other viruses, H5N1 has evolved over time, generating newer versions of itself. In recent years, the predominant version of the virus has spread rapidly among a wide range of animals, but the number of human deaths has declined.
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Associated Press writer María Verza in Mexico City contributed to this story.
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