The World Health Organization has expressed concerns about the spread of H5N1 bird flu, which causes an “extraordinarily high” mortality rate in humans.
An outbreak that began in 2020 led to the death or slaughter of tens of millions of poultry. More recently, the spread of the virus among several mammal species, including domestic livestock in the United States, has increased the risk of spread to humans, the WHO said.
“It remains, I think, a huge concern,” Jeremy Farrar, chief scientist at the U.N. health agency, told reporters in Geneva.
Cows and goats joined the list of affected species last month – a surprising development for experts because they are not considered susceptible to this type of flu. US authorities reported this month that one person in Texas was recovering from bird flu after exposure to dairy cattle, with 16 herds across six states apparently infected after exposure to wild birds.
The A(H5N1) variant has become “a global zoonotic animal pandemic,” Farrar said.
“The big concern of course is that by infecting ducks and chickens and then increasingly mammals, this virus is now evolving and developing the ability to infect humans and then, critically, the ability to pass through to humans. ‘human to human,’ he added.
So far, there is no evidence that H5N1 spreads between humans. But in the hundreds of cases where humans have been infected through contact with animals over the past 20 years, “the mortality rate is extraordinarily high,” Farrar said, because humans have no natural immunity to the virus. .
From 2003 to 2024, 889 cases and 463 deaths caused by H5N1 were reported globally in 23 countries, according to the WHO, bringing the case fatality rate to 52%.
The recent US case of human infection following contact with an infected mammal highlights the increased risk. When “you get into the mammalian population, you get closer to humans,” Farrar said, warning that “this virus is just looking for new, novel hosts.”
Farrar called for increased surveillance, saying it was “very important to understand how many human infections are occurring… because that’s where the adaptation lies.” [of the virus] what will happen”.
“It’s a tragic thing to say, but if I get infected with H5N1 and die, it’s over,” he said. “If I go around the community and pass it on to someone else, then you start the cycle.”
He said efforts were underway to develop vaccines and treatments for H5N1, and stressed the need to ensure regional and national health authorities around the world have the capacity to diagnose the virus.
This was done so that “if H5N1 jumped to humans, with human-to-human transmission,” the world would “be able to respond immediately,” Farrar said, calling for equitable access to vaccines, treatments and diagnostics. .