Bird flu has spiked in parts of the U.S. In Iowa, migrating birds play a role

Since Dec. 6, state and federal officials have confirmed H5N1 at over half a dozen poultry operations with roughly 30,000 to 4.3 million birds. Flocks are culled to prevent the spread of the virus, which is highly contagious and lethal for chickens and turkeys.

In late May and June, H5N1 infected cattle at 13 dairies, along with poultry at three operations in northwest Iowa. But researchers on an Iowa State University Extension webinar on Dec. 17 said it was a different strain.

“The virus we’re seeing right now in Iowa is related to a wild bird strain, and one of the first ways we know what kind of virus is out there — to figure out that link — is to find dead wild birds in the area,” said Yuko Sato, ISU Extension’s poultry veterinarian and a pathologist at the Veterinary Diagnostic Laboratory.

The Iowa DNR recently announced a resurgence of H5N1 in wild birds after nearly a year without detections. Most of the known cases in Iowa have been north of Interstate 80, according to state wildlife veterinarian Rachel Ruden.

Ruden said the DNR detected low-level viral loads in migrating ducks in November. Through its passive surveillance system with the U.S. Department of Agriculture, hunters volunteer samples from bagged birds to be tested.

In early December, the DNR started responding to more sick and dead waterfowl.

Ruden said it’s possible some of the birds picked up H5N1 over the summer, in a breeding range that overlaps with Eurasian flyways.

“And then you bring on the onset of a really significant stress period in a bird's life, when it's traveling and trying to refill and restock and get to where it needs to go for the winter," Ruden said. "And just the sheer number of birds that it's coming into contact with… it kind of creates the perfect storm for an outbreak."

The outbreak this fall doesn't necessarily mean it will happen again in the spring, she added.

Recommendations for the public, hunters, livestock producers

“If you see sick birds in your yard or at the park, keep your pets away from direct contact, and don't handle those birds," Ruden said. "But we still want to hear about them."

The Iowa DNR is asking people who see five or more sick or dead birds within a week to report their findings to their local wildlife biologist or state conservation officer. Signs that a bird may be sick include swimming in tight circles, a twisted head and neck or staying put instead of flying away when approached.

“We’re trying to capture this data as best we can across the state, to understand the scale and scope of the impact of this current outbreak," Ruden said. "And then, where we can, we are trying to mitigate the potential spillover to scavenging species by collecting carcasses."

Carcasses can carry viable viruses for several weeks and infect other wildlife, including bald eagles and red foxes that scavenge on them.

Ruden said backyard birdfeeders are not of concern unless actively attended by waterfowl. The impact on upland birds, like wild turkeys, has also been rare.

Rachel Cramer

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Iowa Public Radio

More than 60 people in the U.S. have had confirmed infections from H5N1 in 2024. Over half have been associated with exposure to infected dairy cows. Around one-third have been connected to poultry operations.

The Centers for Disease Control and Prevention reported the first severe human case from H5N1 in the U.S. on Dec. 18, but says the current health risk to people is low.

Food safety recommendations from the CDC:

• People should not prepare or consume uncooked or undercooked food or related uncooked food products, such as unpasteurized (raw) milk or raw cheeses, from animals with suspected or confirmed H5N1 bird flu virus infection.
• It’s safe to drink commercial milk because products are pasteurized before entering the market. Pasteurization kills bacteria and viruses, like influenza viruses, in milk.
• It’s safe to eat meat and eggs cooked to internal temperature of 165° F.

Hunter safety recommendations from the USDA:

• Wear disposable gloves when handling or cleaning game and wash hands with soap and water immediately afterward.
• Dress game birds in the field whenever possible. If you can’t dress birds in the field, clean them in a location away from poultry and other birds.
• Use dedicated tools and boots for cleaning birds and disinfect after.
• Prevent dogs from interacting with unknown carcasses and avoid feeding them raw meat from harvested birds.

Biosecurity best practices from the USDA and CDC for poultry and dairy producers:

• Wear personal protective equipment.
• Do not touch or consume raw milk or raw milk products, especially from animals with a confirmed or suspected avian influenza A virus infection.
• Only allow people on the farm who need to be there and use one entrance and exit for the farm.
• Isolate sick animals and report them to your veterinarian or state and federal animal health officials.

More about H5N1

Avian influenza viruses are characterized by a combination of “H” proteins, which have 16 types (H1-H16), and “N” proteins, which have nine (N1-N9). The viruses are then classified as “highly pathogenic” if they cause poultry to get sick.

“The H5 and H7 viruses are particularly susceptible to becoming highly pathogenic through mutation from low pathogenic viruses,” Ruden said.

H5N1 was first detected in the U.S. in 2022 and continues to evolve.

In March, the USDA confirmed a strain with a “B3.13 genotype” infected dairy cows in Texas, New Mexico and Canada. Since then, it has spread to other states, often through the transportation of cattle.

This strain has also been the source of some outbreaks at poultry operations, as well as some of the human cases.

California proclaimed a state of emergency on Dec. 18, 2024, in response to a surge of confirmed cases at dairies.