What we know about the deadliest U.S. bird flu outbreak in 7 years

A highly pathogenic bird flu virus is tearing its way through U.S. farms and chicken yards, spreading to at least 24 states less than two months after the first outbreak was reported in a commercial flock.

Nearly 23 million birds have died. It's the worst U.S. outbreak of the avian flu since 2015, when more than 50 million birds died. The outbreak is driving up consumer prices for eggs and chicken meat that, like many costs, had already been rising due to inflation.

Here's what you need to know about the outbreak.

22,851,072 birds have been wiped out

Some birds have died from the disease itself, but the vast majority are being culled to try to stop the deadly and highly infectious virus from spreading. That includes millions of chickens and turkeys in barns and backyards that had been raised to provide eggs or meat.

One of the worst-hit states is Iowa, where more than 5 million birds died at an egg-laying facility in Osceola on March 31, according to the U.S. Department of Agriculture. Overall, more than 13 million birds have been culled in the state.

As of around noon ET on Tuesday, 72 commercial flocks and 46 backyard flocks were reported to be infected around the country.

The bird flu poses only a low risk to humans, the CDC says

It's rare for a human to become infected with the avian virus. No human infections of the highly pathogenic avian influenza (HPAI), which includes the H5N1 bird flu virus, have ever been reported in the U.S., according to the Centers for Disease Control and Prevention.

The virus does not pose a special risk in the nation's food supply, either; the CDC states that like any poultry or eggs, proper handling and heating food to an internal temperature of 165˚F kills any bacteria and viruses present — including any HPAI viruses.

There have been only four human infections of low pathogenic avian influenza (LPAI) viruses ever in the U.S., the CDC says, noting that those cases resulted in only mild or moderate illness.

The virus was first reported in wild birds

The first U.S. warning of the new outbreak came on Jan. 13, when the USDA announced a strain of the highly pathogenic avian influenza virus had been found in wild birds for the first time since 2016. Many of those first cases were in South Carolina and North Carolina, in birds killed by hunters.

The cases then spread north as wild birds migrated and spread the virus to farms. On Feb. 9, an outbreak was confirmed at a commercial turkey flock in Dubois County, Ind.

Ben Slinger, whose family raises turkeys for a meat processor, recently told Iowa Public Radio that he's taking precautions to protect his flocks from infection, after they had to cull tens of thousands of birds in 2015. In addition to using disinfectant, workers wear separate pairs of boots for each barn.

"We know what the aftermath of that is like, and it is pretty disheartening," Slinger said.

Known cases now range from Maine to Texas, where the virus was found in a commercial pheasant flock in Erath County on Sunday.

Grocery prices for chicken are rising

For the current week, the average U.S. price of chicken breasts rose to $3.93 per pound at major supermarkets — sharply higher than last week's $3.14 price. A year ago, the price was $2.48, the Agriculture Department says.

Egg prices have also gone up compared to 2021, and breast tenders cost a full dollar more now than they did a year ago, according to the USDA.

"Prices for white parts are on the rise" with a few exceptions, the department said. "The cost for dark meat items are also increasing; bulk pack drumsticks, thighs, and leg quarters take up most of the spotlight."

The last outbreak lasted about 6 months

The bird flu outbreak that peaked in the late spring of 2015 was "the largest poultry health disaster in U.S. history," the USDA says.

Many of those infections were reported in Iowa and neighboring states near "the intersection of the Central and Mississippi flyways used by wild birds during seasonal migration," the agency said. That's the same region that's now being hit hard by the virus.

In the 2015 outbreak, fomites — objects that can transfer disease — were seen as a key source of viral transmission. Such items include the boots and clothing of poultry industry employees and vehicles used to spread feed. Officials also pointed to the dense concentration of some production facilities as a source of case clusters.

The 2015 outbreak tapered sharply and ended in June of that year — but 3 million birds still died in that final month. Because of the lingering effect on the supply chain, it wasn't until several more months later that some poultry prices peaked and then normalized, according to the USDA.

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