Worst bird flu has moved to Europe but has yet to infect humans

Between 2020 and 2022, something unusual happened with avian influenza.If the most virulent strain breaks out Farms from Asian countries By epicenter, the spread last season was Global and massive. An international team that has been studying epidemiological and genetic data since 2005 has confirmed that the new lineage is now purely African and European.The scientific community (and the livestock industry) is worried about the coming Flu season begins European birds are associated with migrations in the Arctic.

After studying more than 10,000 viral genomes H5 avian influenza, has seen reassortments occur in Europe, converting low-pathogenic variants into more harmful influenza A variants. This could partly explain the mass die-offs of birds and other animals in past seasons.Since the resurgence of the epidemic, at least 250 million poultry were slaughtered. More than 100,000 wild animals have been found dead with the virus in their tissues. Avian influenza has spread to mammals, although infection in humans is rare.

According to the authors, they published their results in naturethe persistence of avian influenza in wild bird populations may be driving Evolution and spread of new strains in Europe and Africa. At present, genetic changes in the avian influenza virus have led to its emergence in many wild species, causing an uncontrollable global epidemic, with Europe being one of the main epidemic centers.

From Asia to Europe: H5N1 influenza outbreak continues

Influenza A H5N1 virus, classified as Highly Pathogenic Avian Influenza (HPAI), It first infected birds in China in 1996, with a mortality rate of 40%.Outbreaks are often seasonal and synchronized with epidemics migrant Autumn in the Northern Hemisphere. But since November 2021, the situation has become persistent, causing damage to the poultry industry and, among other things, pushing up egg prices.

The current work shows that mid-2020An H5N8 strain, which emerged in Egypt in 2016, took an evolutionary “back road.” This led to the emergence of highly pathogenic H5N1 viruses. The new H5N1 avian influenza virus mutated through interaction with non-lethal avian influenza viruses that have been circulating in Europe since 2019.

It developed two subtypes in 2021 and 2022.one of which is distributed throughout the region Nordic coastal areas Eventually reaching North America via the Atlantic migration of birds.The other was taken away by the sea Mediterranean Even Africa. “Once it adapted to wild birds, we had no mechanism to control the virus. I think that’s the biggest impact of the changes happening now,” said co-author Vijaykrishna Dhanasekaran, an evolutionary biologist and virologist at the University of Hong Kong.

“These findings urge the development of systematic control measures for domestic and wild birds to limit virus transmission and control the prevalence of highly pathogenic avian influenza in global avian populations, as well as further research on viral evolution to mitigate and respond to new strains,” ” the authors noted in their study.

A leap to mammals, a warning to humans

Last spring, Adolfo García Sastre (Icahn School of Mount Sinai Hospital), one of the world’s leading influenza experts from New York, explained to Newtral.es that he was worried about the escalation of avian influenza.Usually, it is Almost non-infectious to humans, But infections have also developed in people who were in close contact with infected animals.Specifically, so far in 8 people since 2021:H5N1

One of the most high-profile cases involved a girl from a village in Ecuador who kept infected chickens in her family’s pen. In late 2022, he was close to death. In Spain, a farm worker in Fontanar (Guadalajara) was recorded as asymptomatic H5N1 positive.

It appears to have spread in some non-human mammals, “but it would be a cause for concern if it spread to pigs”

What has not yet been proven is human-to-human transmission. “We will face another scenario,” the virologist warned. The next leap forward, he added.Infections in pigs can be serious”. These animals can become literal “incubators” and mixers for new, more pathogenic influenzas that can multiply in humans, as happened with the 2009 influenza A pandemic.

this Influenza A is usually the most common In recent seasons it has been held in Spain every autumn and winter. It is a flu that originated in birds but has adapted to humans without causing serious damage. There are many subtypes and variants within category “A”. But the H5N1 virus is not common at all. The problem is that the genetic changes triggered by numerous infections in birds and mammals eventually adapted them to their human hosts.

INIA-CSIC researcher Gustavo del Real believes that these restructurings are what we should be most worried about. “These new highly virulent H5N1 viruses are spreading globally through Recombination with other strains Research from Spain’s SMC highlights the impact of low-pathogenic avian influenza in wild and domestic poultry. He therefore joins the authors in advocating “urgent implementation of systematic control measures for domestic and wild birds to limit the emergence of new epizootics and prevent their spread to mammals, including humans,” he concludes.

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