Scientists race to decode secrets of deadly bird flu

The worst avian flu outbreak in the nation's history has spawned a series of investigations by Minnesota disease researchers to figure out why this new and exceptionally deadly virus is behaving in such bizarre ways.

Because at this point, scientists are baffled.

"This situation is throwing all the old dogma out the window," said Michael Osterholm, an infectious disease specialist at the University of Minnesota who advises the turkey industry.

U scientists and others are racing to find answers that could determine the future of the poultry industry, an $800 million piece of the state's economy, and help manage the nation's food supply.

The outbreak, which has so far decimated poultry operations and sent egg prices soaring, also provides a stark warning that flu viruses are unpredictable and can swiftly mutate from benign to dangerous. This strain has been moving around the globe for years, crossing and mixing among many species of birds — proving lethal to some and relatively harmless in others. And though it presents a very low risk to people, no one knows if or when that could change.

"If there is any disease that's incredibly humbling, it's influenza," Osterholm said. "Every time you think you know it, you are reminded that Mother Nature is in charge."

In one study, a complex project patterned after foodborne illness investigations, U scientists are interviewing managers from 60 Minnesota turkey farms to find out why some operations were infected and others are not. Other researchers are examining whether the virus travels by air, and, if so, how far it can go. And the U.S. Department of Agriculture is working on a vaccine.

This outbreak is, in a sense, a continuation of one that began in China in 1996. The virus stayed there for seven years, but then began an unprecedented spread across Europe and Africa. It has changed over time, affecting both wild and domestic birds, but genetic testing shows that the H5 component that arrived in Minnesota has Asian lineage, said Suarez.

The virus first showed up in this country in wild birds moving along the Pacific flyways late last year, Suarez said. Wild birds are usually the carriers as bird flu spreads, serving as a permanent reservoir and genetic mixing pot.

What sets this one apart is that it was found in large numbers of wild waterfowl, Suarez said. And unlike most flu viruses found in wild birds, this one was "highly pathogenic," meaning that it makes domestic birds really, really sick.

"Now we have a high pathogenic virus in wild birds that jumped to domestic [flocks] and caused a highly pathogenic outbreak in domestic poultry," he said.

It first touched down in the West, then in March it showed up in Minnesota — the heart of the nation's turkey industry — again most likely carried by migrating water fowl. Here, it roared through domestic poultry flocks with breathtaking speed.

Initially, farmers and scientists assumed it was spreading from wild birds into the poultry barns. And, in some cases, that was likely. But the rapid spread from barn to barn and farm to farm was unprecedented in this country, though similar to some outbreaks in others.

"It could have been introduced" in wild birds, Osterholm said. "But there is something else amplifying it."

Figuring that out has taken Montserrat Torremorell, an associate professor of veterinary medicine at the U, to six infected poultry farms in Iowa, Minnesota and Nebraska.

Torremorell and her colleagues are expert at detecting the genetic material from a virus in the air. They normally work with swine operations, but were recruited to address the rising concern that somehow this avian flu is spreading by air in addition to physical contact.

At five of the six farms, in the midst of sick and dying birds, she and her colleagues have found the virus inside barns and immediately outside. But so far they have not found it at extended distances outside the barns.

Mostly, it depends on what it sticks to.

"Viruses don't have wings," she said.

They can stick to feathers, dust, feed, water droplets, dried fecal material, truck tires and the soles of shoes. To solve that mystery, scientists also need to understand how the poultry industry functions. And poultry operations that produce hundreds of thousands of turkeys or contain millions of laying chickens are extraordinarily complex. They don't have one truck, they have a dozen. There isn't one person collecting eggs, there are many.

The emerging evidence that this flu does move by air is already changing the thinking about how to control it, Osterholm said.

"The old model for looking at containment was the concentric circle model," he said. But if this virus can move with the wind, even for short distances, then it moves in a plume like smoke. A farm that is next door but upwind could be safer than one downwind and farther away.

It may also change the industry's strategies for biosecurity. Scientists from the U are now surveying 60 Minnesota turkey operations that are owned by or supply birds to Hormel Foods' Jennie-O Turkey division. Half the farms were infected, and half were not. The question: what made the difference?

Researchers are using a 20-page questionnaire much like the ones used to trace food-borne illnesses like salmonella back to the original source. It focuses on activity in the days before the infection erupted: Who visited? Were there birds in the barns? How is the litter managed?

"You can imagine how difficult it is," said Jeff Bender, a U vet school professor and one of the project's leaders.

The outbreak is already amping up public debate about the nation's food system and its vulnerability to infections.

"To me, it's a discussion of how do we manage the food supply to decrease the risk," not just for disease, but for the industry's bottom line and the stability of the food system as well, said Torremorell.

"Because these viruses are very smart," she said.

Josephine Marcotty • 612-673-7394