JUANA SUMMERS, HOST:
An unprecedented number of people in the U.S. were infected with bird flu this past year. In this country, a lot of science focused on the virus in dairy cows and in poultry. But researchers say something ominous is happening in wild animals and not just birds. NPR's Gabrielle Emanuel reports.
GABRIELLE EMANUEL, BYLINE: Last year, Marcela Uhart was walking on a beach in Argentina, the Punta Delgada. Travel guides boast of its rich marine wildlife. But the scene that she saw was not idyllic. It was a horror scene.
MARCELA UHART: The beaches were just loaded with carcasses. We estimate about 18,000 dead baby elephant seals.
EMANUEL: Dead from bird flu. Uhart is a researcher. She studies wildlife health at the University of California Davis. She came to this beach because she's been tracking bird flu as it goes from one bird species to another - pelicans to terns to other seabirds and then spills over into marine life and then back to birds. When Uhart was standing on that beach, she says she could see birds stumbling around, having seizures on the sand. If she looked up?
UHART: It was just, like, birds flying, you know, falling out of the sky dead. So, yeah, I mean, it is very dramatic. It is very dramatic.
EMANUEL: Dramatic and worrisome because what she saw was evidence that this very deadly virus had found a way to travel and fast.
UHART: It's like wildfire. I mean, it just killed everything it encountered. We were all skeptical that this could be possible, but then somehow this started happening with this virus.
EMANUEL: Now, this virus, H5N1, it's been around for decades. It originated in East Asia, infecting poultry and sometimes people. And it did periodically jump over into wild birds. But the virus killed them quickly before they could migrate, so the virus never took off globally. Then about five years ago, the virus changed. Erik Karlsson is the director of the Cambodian National Influenza Center.
ERIK KARLSSON: This new virus seems to be a bit more like dead bird flying, right?
EMANUEL: So a bird gets infected and will likely die eventually, but first...
KARLSSON: They seem to be able to still migrate further, and they contact another group of birds. They fly a little bit further, and that eventually gets all the way across the world.
EMANUEL: It's almost like a relay race. And that's what Michelle Wille has been mapping. She's at the Centre for Pathogen Genomics at the University of Melbourne. She says infected wild birds carried the virus to North America a few years ago, and then South America.
MICHELLE WILLE: So then in South America, it traveled the 6,000-kilometer spine in about six months, OK? So this is a virus. It's not assisted by airplanes. This is a virus that's traveling by mass mortality after mass mortality, after mass mortality, after mass mortality.
EMANUEL: Now, she says, the virus is racing around Antarctica. The problem globally is nobody knows how many wild animals the virus has killed.
WILLE: No one's counting. We have no idea. So it's been like a catastrophe. It is a global catastrophe.
EMANUEL: It's a catastrophe for the animal species and for the ecosystems they're part of. But on top of that, this matters for human health. People can get bird flu. But right now, the virus doesn't spread easily from one person to another. That could change. The estimates are millions of birds have been infected and tens of thousands of marine mammals. And each animal the virus infects, that's another chance for it to evolve. Flu viruses, including bird flu, are known for lots of genetic changes.
WILLE: So as they've gone to new places, they've mixed and matched their genes with one of their normal influences. The resulting virus could be sort of Frankenstein of those two things.
EMANUEL: Scientists say this makes it particularly important for people to know what's happening in the animal world. That way we can know what the virus might do in the human world next.
Gabrielle Emanuel, NPR News.
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