Perhaps we can blame COVID fatigue for numbing us to the risks of other viruses. But it should be bigger news that a bird flu has mutated to spread through mammals and is ominously appearing among wild and domesticated animals around the globe.
In the past, the inability to spread from one mammal to another was the barrier that prevented bird flu, H5N1 — which has a 50 percent fatality rate in humans — from becoming a human pandemic. It’s not clear this version, which spread through minks, would be easily transmitted in people, but it has made a step in a dangerous direction.
One reason there so many dangerous animal viruses around now is that the crowded conditions of mass-farmed animals tend to spread viruses — and there has never been more worldwide demand for meat, dairy products and eggs. As one investigation revealed, egg-laying chickens in big operations are genetically identical, have no immunity to influenza and make easy kindling for viral bonfires.
While it might cost money to move to safer chicken farming practices, doing nothing is expensive, too. Last year, egg prices rose as 58 million U.S. birds were destroyed in H5N1 outbreaks.
The outbreak that has spurred the latest fears happened at a mink farm in Spain. “The fact that it spread through the facility is quite concerning,” said Jeff Bender, a professor of veterinary medicine at the University of Minnesota.
In this case, the surveillance system worked — the outbreak was identified, people were tested and found to be negative, and more than 50,000 minks were euthanized. But it’s not clear all farms around the world are under good surveillance.
“We’re getting better but there’s a value for integrating surveillance systems,” Bender said. “We’ve been talking about improving it, but there’s a long way to go.”
Mink farms may pose a pandemic risk that’s not worth having. They aren’t a source of food — and there are safer sources of fur. And unlike most farm animals, they are carnivores and can pick up viruses from the animals they are fed.
H5N1 has a natural host in wild waterfowl, and some of them carry the virus around the globe with their migrations. It was first discovered to be capable of jumping to humans in the 1990s, and has been bubbling up around the world ever since. What’s worrisome now is that it’s getting into so may new hosts — eagles, owls, as well as foxes, bears and seals.
Most bird influenza isn’t equipped to get into the cells of mammals, but this virus is what scientists call promiscuous. “If it’s transmitted to mink, it hasn’t had time to be a mink-specific thing — so there’s a good chance it can go to humans,” Purdue University virologist David Sanders said.
Sanders said the deadly 1918 flu pandemic started with a bird flu that jumped to humans, and the 2009 swine flu was a descendant of this virus, having jumped from humans to pigs in the 1920s before jumping back to humans.
As a point of counterintuitive reassurance, Sanders said that if H5N1 did start spreading in humans and it remained 50 percent lethal, it might be more easily contained, like SARS1 was in 2005. The COVID-19 pandemic is being fueled by a combination of transmission before symptoms start and people who get such minimal symptoms that they have no idea they’re sick while they circulate and spread disease.
Plus, we already have a vaccine for H5N1, although it would take months to scale up production.
Even so, why wait to find out how deadly a human H5N1 pandemic would be? Cost-saving measures and mass farming already gave us foot and mouth disease and mad cow disease. And from the point of view of a virus, we humans, with our urban lifestyles, are just the equivalent of captive animals in one vast, interconnected worldwide farm.
Faye Flam is a Bloomberg Opinion columnist covering science. She is host of the “Follow the Science” podcast.
