New cases of bird flu appear to be on the wane, after costing U.S. poultry farmers more than 48 million birds.
But even as outbreaks taper off, experts still are puzzling over why the virus wreaked such havoc, upending the livelihood of farmers like Becky Bruns.
About a month ago, Bruns thought she was going to dodge the bird flu crisis at her pullet farm in Danube, Minn. She thought if she could just make it to June without the virus hitting her farm, the chance that her flocks would get infected would drop dramatically. Experts believed the virus wouldn't survive in warm weather.
Meanwhile, Bruns ramped up biosecurity measures on her farm, like spraying her barns' air inlets with disinfectant.
“Every week we had a meeting, we had our little pow-wow session to say: ‘What are we doing? What are we missing? What more could we do? Where could it get in that we're not thinking of?’” she says.
An egg production company owns the birds. Bruns cares for them from the day they hatch until they're old enough to lay eggs. She says she loves the baby birds.
So she was devastated when bird flu did hit on June 1st, the point at which she thought she'd be in the clear. The USDA deployed crews with equipment to euthanize her birds.
“To have it come in after that much work was just heartbreaking,” she says. “And it just felt like such a huge failure on our parts.”
What should Bruns have done differently? Experts don't have clear answers. Much about bird flu still stymies them.
They think waterfowl brought the virus to the Midwest. But was it wild birds? Domestic ducks?
“A few months ago, I thought by this time I'd be able to tell you that. It's more of a mystery today than it was before, except that we know it's one of the species,” says Carol Cardona, a bird flu expert at the University of Minnesota.
Epidemiologist are looking at not just what introduced the virus, but also what spread it and sustained it.
“Each one of those might be a very different source. And therefore we're going to have to understand all of them,” says Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.
Just last week, the USDA published a report on bird flu, pretty much saying, “Still working on it. Got some theories. Nothing definitive."
It said the virus might travel on people or trucks that move between farms. Wind might blow the virus from one farm to another.
“What I think is also possible is that the air, when it leaves the facility, it contaminates the surrounding of the facility,” says Montse Torremorell with the College of Veterinary Medicine at the University of Minnesota.
Torremorell says the dust or equipment the virus particles land on might then ferry the virus elsewhere.
"Do we need to make these buildings much more airtight and the air be filtered? That in fact could be a possibility,” says Osterholm.
Osterholm expects bird flu will reappear, a pattern in other countries. That prospect is unnerving to Becky Bruns. She's trying to figure out if it makes sense to keep her family business going in light of future threats. They've raised chickens for 35 years.
“Is this going to stop?” she asks. “Am I going to be bringing birds in just for them to get sick again?"