When Larry Pouliot went on a morning walk in Sitka National Historical Park on May 9, he spotted a lethargic, unresponsive bald eagle perched in a tree, its eyes bloodshot and its neck drooping.
“I realized he was not doing great,” said Pouliot, who got video footage and photos of the ailing bird.
He called the Alaska Raptor Center, a local bird rescue and rehabilitation facility. Within a couple of hours, Pouliot said, center responders who had been summoned to the site watched the eagle fall from the tree. It then died.
That was a confirmed case of the highly pathogenic avian influenza that has swept through poultry farms and wild bird populations worldwide and moved westward from the Atlantic coasts of Canada and the United States.
The arrival in Alaska of this unusually lethal strain, first confirmed last month by a case in a backyard chicken flock in the Matanuska-Susitna Borough and later documented among wild birds from the Aleutians to southeast Alaska, is a potentially ominous sign for the rest of the world.
Why avian influenza in Alaska is a problem
Alaska is both a reservoir and a distribution hub for avian influenza viruses. Each year, millions of birds migrate here from Asia, North America, South America, Australia and even Antarctica, converging to feed and breed in the near-continuous daylight. They crowd together, creating opportunities for viruses to exchange genetic material and get rearranged.
“Mutations can mix things up, quite literally, so that’s a concern,” said Andy Ramey, a U.S. Geological Survey wildlife geneticist who is an expert on avian influenza. Come fall, “as birds disperse, they can bring viruses with them, leading to outbreaks in new areas or new regions.”
The part of the world that scientists call Beringia – which encompasses the spot where Alaska nearly touches Siberia – is the usual pathway for Asian avian influenza viruses to enter North America. That was the case in 2014 and 2015, the last time a wave of highly pathogenic virus swept through U.S. and Canadian bird populations.
This time, the virus – linked to the Guangdong strain first identified in China in 1996 — appears to have moved west and been carried to the East Coast over the Atlantic. It was documented last year in the eastern Canadian provinces and possibly carried through an unusual assemblage of birds in that part of the world. By now, Ramey said, it is likely that the virus is moving around the world through various pathways and in various directions.
Along with Alaska’s geographic position as the bullseye for several migratory bird flyways, the state has other characteristics that make it a globally significant avian influenza site.
“The one thing about influenza viruses, especially avian influenza viruses, is they like a wet and cold environment,” said Bob Gerlach, Alaska’s state veterinarian.
Ramey’s research has found that influenza viruses can survive for more than a year in Alaska’s wetlands.
While wild birds in Alaska and elsewhere commonly carry low-pathogenic virus strains, which generally cause little harm, the spread within the wild population of high-pathogenic viruses is a significant change from the past, Ramey said.
Until now, only one case of a wild Alaska bird
Until about 20 years ago, highly pathogenic avian influenza viruses were thought to be solely a problem for domestic poultry. Before 2002, there was only one documented case of a wild bird infected with a highly pathogenic virus, he said. And until now, the sole documented case of a wild Alaska bird infected with a highly pathogenic virus came from a mallard found in 2016 in Creamer’s Field in Fairbanks.
“So this is kind of new territory,” Ramey said. “Now we have high-path influenza that’s persisting and being maintained in wild birds.”
Just why that is happening is the subject of much research. Some scientists have warned that climate change, which is accentuated in Alaska, is shifting migration patterns and creating new assemblages of bird species in their Beringian summer gathering sites, thus increasing the risks of influenza spread.
For now, it appears unlikely that this influenza will have population-level effects on Alaska’s wild birds, Ramey said.
So far, known infections in Alaska are mostly among eagles and Canada geese. Raptors seem to be vulnerable, in Alaska and elsewhere, possibly because they are eating sick or dead birds that carry the virus, Ramey said.
Avian influenzas are generally more common among waterbirds found in freshwater systems – geese, ducks and swans – than in seabirds, including those species that have been hit by successive years of die-offs in the Bering Sea region, he said.
There are 28 Alaska species that the USGS, though its past work on avian influenza, has designated as high priority for monitoring.
As for the sightings of sick and dead birds to date, eagles and geese may be dominating simply because they are the most visible birds, Gerlach said. “Some of these other dabbling ducks are small, and if they do die and get swept to the side they may not be as noticeable,” he said.
The arrival of highly pathogenic influenza right after the bird die-offs is unfortunate, even if some species are more vulnerable than others, Gerlach said. “In this case, this is another stressor on the population, and what impacts it’s going to have will be really unknown,” he said.
Jumping across species
Also yet unknown is how this strain might spread beyond birds.
Avian influenzas have jumped across species in the past, including to marine mammals, Gerlach pointed out. This year, federal biologists will be looking for the virus in Alaska’s marine mammals, he said.
There is already precedent for this virus to spill over into mammals. Foxes in the upper Midwest and Canada have been found with this virus, including a kit found dead in Ontario.
In Alaska, biologists will be watching this year for potential spread to marine mammals, among other animals, Gerlach said.
As for humans, so far only two people have tested positive for this avian influenza, one in the United Kingdom and one in the U.S., according to the Centers for Disease Control and Prevention.
It is rare for avian influenza viruses to harm human health, experts say. But when that happens, the results can be devastating.
The deadly pandemic that started in 1918 and killed at least 50 million people was caused by a virus that originated in birds, scientists say. More recent severe influenza pandemics have also been caused by avian viruses, including the 1957 Asian flu and the 1968 Hong Kong flu, according to the CDC.