Perhaps COVID-19 fatigue can be blamed for numbing people 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 is not clear whether this version, which spread through minks, would be easily transmitted among people, but it has made a step in a dangerous direction.
It is unthinkable to consider lockdowns or mask mandates over some new disease, which is why it is better to take simpler, less costly action early. What matters now is surveillance among farmed animals and giving up particularly dangerous practices. Maybe people just cannot have mink coats and cheap eggs.
One reason there are so many dangerous animal viruses around 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 found, 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 US 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.
However, it is not clear whether all farms around the world are under good surveillance, and since getting a positive test means being forced to kill valuable animals, farmers might have an incentive to avoid it.
“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 might pose a pandemic risk that is not worth having. They are not a source of food and there are safer sources of fur. They are typically raised in close quarters, and unlike most farm animals, they are carnivores and can pick up viruses from the animals they are fed.
Farmed minks sometimes get fed discarded chicken carcasses, which can harbor H5N1, Bender said.
There are also plenty of opportunities for people working on mink farms to get infected. In a worst-case scenario, a worker would pick up a variation of this virus capable of moving from human to human.
“That’s exactly the pandemic scenario we worry about,” Bender said.
It is not yet clear whether multiple animals picked up the virus separately from a contaminated batch of food, but researchers have found that the virus emanated from a couple of hotspots, indicating that one or two infected animals likely spread the disease to their neighbors.
Genetic tests showed that this virus carried a mutation that allows it to spread in mammals, as well as one that has been identified in gulls.
That suggests gulls are still carrying this concerning variant.
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 southern China and Hong Kong in the 1990s, and has been bubbling up around the world ever since.
What is worrisome now is that it is getting into so many new hosts — eagles and owls, as well as foxes, grizzly bears and seals.
In birds, H5N1 is a gastrointestinal virus, spread by droppings, but it can become a respiratory virus in mammals, Purdue University virologist David Sanders said.
The gastrointestinal tracts and respiratory tracts are similar enough that the virus can adapt easily from one to the other.
Most bird influenza is not equipped to get into the cells of mammals, Sanders said.
However, this bird flu 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,” he said.
So far, no version that can spread from human to human has been seen, but only by pure luck.
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, Sanders said.
Likewise, there is still a school of thought that the Omicron variant of SARS-CoV-2 acquired its large number of mutations by jumping from a human to another animal and then back to humans.
As a point of counterintuitive reassurance, Sanders said that if H5N1 did start spreading in humans and remained 50 percent lethal, it might be more easily contained, as SARS-CoV-1 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 are sick while they circulate and spread disease. By staying in the upper respiratory tract, Omicron is also even more wildly contagious than its predecessors.
So there is no guarantee that an H5N1 pandemic would be “even deadlier” than SARS-CoV-2. Plus, there is already 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 the world foot and mouth disease and mad cow disease.
From the point of view of a virus, 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.
This column does not necessarily reflect the opinion
of the editorial board or Bloomberg LP and its owners.
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