Three global health groups today warned that, with H5N1 avian flu outbreaks continuing to devastate animal populations and increasing detections in mammals, the virus could adapt to more easily infect humans.
The joint statement came from the UN Food and Agriculture Organization (FAO), the World Health Organization (WHO), and the World Organization for Animal Health (WOAH). They urged countries to work together across sectors to protect both animals and people.
The culprit is the H5N1 clade 2.3.4.4b, which began circulating in 2020 and has caused unprecedented deaths in wild birds and poultry, first in Africa, Asia, and Europe, then in North America and Central and South America. After 67 countries reported outbreaks in 2022, 14 more reported outbreaks this year, mainly in the Americas.
Alarming rise in mammal cases
Wild birds have been hit hard by mass deaths, and reports of deadly outbreaks in mammals are now on the rise. So far, 26 mammal species have been infected, and since 2022 WOAH has received reports of outbreaks in mammals from 10 countries across three continents, most recently in Polish cats.
There is a recent paradigm change in the ecology and epidemiology of avian influenza which has heightened global concern.
Gregorio Torres, DVM, who leads WOAH's science department, said, "There is a recent paradigm change in the ecology and epidemiology of avian influenza which has heightened global concern as the disease spread to new geographical regions and caused unusual wild bird die-offs, and alarming rise in mammalian cases."
Labs track mutations, potential clinical impact
Human cases remain sporadic and linked to people who had close contact with infected birds and their environments. Of eight cases reported, some were severe or fatal.
Sylvie Briand, MD, the WHO's director of epidemic and pandemic preparedness, said the WHO is working closely with the FAO, WOAH, and lab networks to monitor virus evolution and look for any changes that would the virus more dangerous to humans. "We encourage all countries to increase their ability to monitor these viruses and to detect any human cases. This is especially important as the virus is now affecting countries with limited prior experience in avian flu surveillance."
In today's joint statement, the groups also detailed the most current virus assessments. For example, a marker detected in the PB2 gene of H5N1 viruses from mammals are known to increase virus replication in mammalian cells. Though none of the changes seen show increased preference for binding to human-like receptors, some mutations have given the virus an increased ability to do so.
We encourage all countries to increase their ability to monitor these viruses and to detect any human cases.
The H5N1 viruses isolated from minks have a genetic mutation that allows better replication in mammal cells, and samples from minks—and some birds—have extra mutations more commonly seen in human viruses.
Scientists have also been gauging the susceptibility of the circulating H5N1 viruses to antiviral drugs. So far, samples from human cases show no markers for resistance to neuraminidase inhibitors such as oseltamivir or endonuclease inhibitors such as baloxavir.
Viruses from animal species showed only sporadic mutations linked to antiviral resistance. And researchers expect that people would have minimal population immunity to the hemagglutinin of the current H5N1 virus.
France picks poultry vax maker as birds in Sweden infected
In other developments, France—the first European Union country to vaccinate poultry against avian flu—has tapped Boehringer Ingelheim to supply 80 million doses to immunize ducks, Reuters reported today.
Source : umn.edu