A Mexican man has died from a type of bird flu, but U.S. officials remain focused on another strain.

new york – In Mexico, some Avian influenza Experts say the outbreak is unrelated to another type of infection that has occurred on US dairy farms.

Here we look at this case and the types of avian influenza.

A 59-year-old man in Mexico who was bedridden due to chronic health problems developed fever, shortness of breath and diarrhea in April. He died a week laterand the World Health Organization reported it this week.

The WHO said this was the first time that this strain of bird flu (H5N2) had been identified in humans.

Another strain of bird flu, H5N1, has infected poultry flocks over the past few years, leading to the culling of millions of birds, and is spreading to all kinds of animals around the world.

This year, the flu was detected American Dairy FarmsDozens of herds have been infected, and recently Iowa and Minnesota.

The spread of infection in cattle is Three illnesses reported One farm worker, one in Texas and two in Michigan – all with mild symptoms.

Their emergence in animals and humans is of concern because so-called influenza A viruses are the only viruses associated with human influenza pandemics. These viruses are classified into subtypes based on the types of proteins on their surface: hemagglutinin (H) and neuraminidase (N).

Scientists say there are 18 different H types and 11 different N types that appear in various combinations. H1N1 and H3N2 are the common causes of seasonal influenza in humans. Many versions are also found in animals.

The H5N1 strain that has recently worried US scientists has historically been found mainly in birds but has recently spread to a wide variety of mammals.

The H5N2 virus has previously been identified in poultry in Mexico, and farms are vaccinated against it.

This is not unusual in the United States: In 2004, 7,000 chickens in south-central Texas were infected with H5N2 influenza, the first time in 20 years that the US had seen an outbreak of avian flu that was dangerous to poultry.

H5N2 was also the primary cause of the wave of outbreaks that occurred on commercial poultry farms in the United States in 2014 and 2015.

For many years, H5N2 has oscillated between a mild and severe threat to birds, but was never considered a threat to humans.

A decade ago, researchers used mice and ferrets to study a strain of the virus then affecting U.S. poultry and concluded it was less contagious and less deadly than H5N1, and officials said there was no evidence it was spreading among humans.

Rare cases of infection in animals are reported each year, so it is not surprising that humans have been diagnosed with H5N2 virus infection.

“An optimistic person would say, 'This system is doing exactly what it was designed to do, which is to detect and document rare human infections that we were groping around in the dark about a few years ago,'” said Matthew Ferrari, director of the Center for Infectious Disease Dynamics at Pennsylvania State University.

In fact, Mexico's Health Minister Jorge Alcocer said the man died of kidney and respiratory failure, not the virus.

Some experts said it was noteworthy that it was unclear how the man contracted H5N2.

“The fact that he had no reported contact (with infected birds) raises the possibility that he was infected by someone visiting him, but it's too early to jump to such a conclusion,” said Richard Webby, an influenza researcher at St. Jude Children's Research Hospital in Memphis.

At present, H5N2 is still considered to be a lesser threat than other types of avian influenza. Most human illness is attributed to the H7N9, H5N6 and H5N1 avian influenza viruses.

Five outbreaks of H7N9 are believed to have killed more than 600 people in China between early 2013 and October 2017. And at least 18 people have died in China in 2021 from an H5N6 outbreak, according to the U.S. Centers for Disease Control and Prevention.

The H5N1 virus was first identified in 1959 but did not cause much concern to health authorities until an outbreak in Hong Kong in 1997, causing severe illness and death.

Cases of the H5N1 virus continue to occur, mostly through direct contact between humans and infected animals. According to WHO statistics, there have been more than 460 confirmed deaths worldwide since 2003, and nearly half of reported cases are likely to be fatal.

Like other viruses, H5N1 has evolved over time, spawning new versions. Over the past few years, the predominant version of the virus has spread rapidly among a variety of animals, but has caused fewer human deaths.

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Associated Press writer Maria Berza in Mexico City contributed to this report.

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