What we know about the deadliest U.S. bird flu outbreak in history - NPR

The U.S. is enduring an unprecedented poultry wellness disaster, with a highly contagious vertebrate flu microorganism triggering the deaths of immoderate 52.7 cardinal animals.

The culprit is highly pathogenic avian influenza, oregon HPAI. It has ravaged workplace flocks and chickenhearted yards successful 46 states since February, erstwhile the archetypal cases were reported successful commercialized flocks.

It's the worst toll connected the poultry manufacture since 2014-2015, erstwhile much than 50 cardinal birds died. That earlier outbreak besides started successful the wintertime — but portion that ordeal was implicit by the pursuing June, the existent outbreak lasted done the summertime and has surged anew.

"I'm hopeful that this is not the caller mean for us," Dr. Richard Webby, manager of the World Health Organization's Collaborating Center for Studies connected the the Ecology of Influenza successful Animals, tells NPR.

Some birds person died from the illness itself, but the immense bulk are being culled done flock "depopulation," to effort to halt the microorganism from spreading. That includes millions of chickens and turkeys successful barns and backyards that had been raised to supply eggs oregon meat.

Here's what you request to cognize astir the 2022 outbreak successful the U.S.:

52,695,450 cardinal birds person been wiped out

The losses agelong crossed the U.S., and they're deepest successful the country's middle: More than 1 cardinal birds person been killed successful each of 11 states that agelong from Utah to the Midwest and connected to Delaware, according to the U.S. Department of Agriculture.

In Iowa, 2 monolithic egg-laying operations had to cull much than 5 cardinal birds successful azygous incidents earlier this year.

Unlike the 2014-15 outbreak, this 1 is being driven by wild birds, not by farm-to-farm transmission. For commercialized and backyard flocks, galore aboriginal infections centered on the intersection of the Central and Mississippi flyways of migratory chaotic birds. As those birds traveled, truthful did the virus.

"We don't cognize precisely what it is astir it, but it does look conscionable to beryllium capable to turn and transmit amended successful chaotic birds," Webby, who is besides a subordinate of the infectious diseases section astatine St. Jude Children's Research Hospital successful Memphis, tells NPR.

"Wild birds are the cleanable mechanics to dispersed a microorganism due to the fact that they, of course, alert everywhere," helium adds.

Influenza viruses are communal among chaotic aquatic birds, which often amusement nary symptoms contempt being infected. In January, the unsafe H5N1 flu microorganism was recovered successful an American wigeon duck successful South Carolina — the archetypal U.S. lawsuit since 2016, according to the Centers for Disease Control and Prevention. More reports poured successful implicit the pursuing weeks and months, raising alarms arsenic the microorganism dispersed to much states.

A highly pathogenic avian influenza microorganism "can origin illness that affects aggregate interior organs with mortality up to 90% to 100% in chickens, often wrong 48 hours," the CDC notes. "However, ducks tin beryllium infected without immoderate signs of illness."

Avian flu poses lone a debased hazard to humans

It's precise uncommon for a quality to beryllium infected with the avian virus. The archetypal U.S. lawsuit of a idiosyncratic infected with avian influenza A (H5N1) microorganism was reported successful April successful Colorado. The diligent recovered aft experiencing a fewer days of fatigue.

The microorganism does not airs a peculiar hazard successful the nation's nutrient supply, fixed due handling. The CDC states that similar immoderate poultry oregon eggs, heating nutrient to an interior somesthesia of 165˚F kills immoderate bacteria and viruses present, including HPAI viruses.

The microorganism is similar a kid successful a candy store

"The vertebrate populations haven't seen viruses similar this before," Webby says, "so successful presumption of their immune response, they're each immunologically naïve to this" influenza virus.

"Right now, it's similar a kid successful a candy store racing around," infecting vertebrate populations, helium says.

U.S. experts had been bracing for an outbreak, watching palmy strains of the H5N1 influenza microorganism proliferate successful Europe and elsewhere. Now that the microorganism is here, it shows nary motion of going away.

A cardinal portion of the challenge, Webby says, is that similar the SARS-CoV-2 virus, the avian flu microorganism has spun disconnected respective variants of concern. And close now, a circumstantial mentation of the microorganism — known arsenic clade 2.3.4.4b — is ruling the roost.

"You tin deliberation of that similar an omicron variant" due to the fact that of its wide prevalence, Webby says.

Viruses are notoriously quick to mutate. And since its accomplishment successful North America, the avian influenza microorganism has continued to change.

"When the microorganism came implicit into the Americas, it started to interact with the viruses that we person successful our chaotic birds here," picking up antithetic combinations of different genes, Webby says.

Comparing the existent U.S. microorganism to the 1 successful Europe, Webby says, "From the extracurricular looking in, they look precise similar. But erstwhile you really spell connected the wrong and instrumentality a look, the viruses we person present are rather antithetic present from what was successful Europe."

It's imaginable that chaotic vertebrate populations volition physique up an immunity to the microorganism — but Webby warns that it volition instrumentality months to recognize whether that is happening astatine a meaningful level.

The outbreak hasn't raised each poultry costs

If you similar to devour chicken, you're successful luck. This mentation of the influenza microorganism doesn't impact "broilers" — chickens raised for nutrient — arsenic severely it does "layers" — table-egg laying hens — and turkeys.

"For immoderate reason, turkeys and furniture birds thin to beryllium much susceptible" to the virus, says Amy Hagerman, an adjunct prof astatine Oklahoma State University who specializes successful cultivation economics.

"The chickenhearted that astir radical deliberation of, their chickenhearted tenders, their chickenhearted sandwiches, each of those things haven't tended to person the aforesaid kinds of impact," she adds.

Hagerman warns that successful a clip of inflationary pressure and supply-chain snags, it tin beryllium hard to straight nexus a terms hike to the virus. But she notes that U.S. ovum prices tin beryllium affected if conscionable a fewer farms person to dispose of their flocks.

"Generally speaking, these complexes are implicit a cardinal birds, easily," Hagerman says. "It takes less egg-laying operations being affected by HPAI to thrust up the terms of eggs and ovum products," she adds, particularly since the bulk of U.S. accumulation goes to the home market.

The microorganism has deed galore turkey farms — but due to the fact that those operations thin to beryllium smaller and the cases person been dispersed retired implicit clip and space, producers person mostly been capable to sorb the losses, gathering up stocks of frozen turkey up of the end-of-year holidays.

"So, yes, we surely saw an summation successful turkey prices successful this vacation season," Hagerman says, "but not arsenic overmuch arsenic we mightiness person anticipated fixed the grade of this outbreak."

What astir vaccines?

The beingness of the microorganism successful the commercialized nutrient concatenation raises a fig of imaginable commercialized headaches — but truthful would utilizing a vaccine to combat it.

"A batch of countries don't usage vaccines for this microorganism successful their poultry," Webby says.

"One of the large complications is timing connected a vaccine," Hagerman says. "Generally you request 2 doses of a vaccine and past a magnitude of clip to execute afloat effectiveness."

"If you person a vertebrate that has a precise abbreviated feeding model earlier it's acceptable for harvest, that tin beryllium a batch much challenging due to the fact that you besides request to let the withdrawal play aft the vaccine earlier the vertebrate is harvested," she adds.

Another cardinal contented is the trouble of surveillance — of knowing whether a vertebrate is infected with a deadly influenza microorganism but isn't showing symptoms due to the fact that they've been vaccinated.

But the calculations mightiness alteration if the microorganism is determined to beryllium endemic successful chaotic birds oregon successful a geographic area.

That "certainly seems to beryllium the lawsuit successful Europe and Africa," Webby says, adding, "my gut feeling is we're headed that mode successful the Americas arsenic well."

"These are really discussions that are going connected now," Webby says, describing ideas specified arsenic what benignant of post-vaccination surveillance would beryllium needed to "make definite your trading partners are blessed that the microorganism is not circulating silently."

The past outbreak didn't past the summer. This 1 did

Experts accidental poultry farms should beryllium credited with limiting the microorganism arsenic overmuch arsenic they have, hailing the occurrence of surveillance and biosecurity programs. But astir 11 months aft the archetypal known chaotic lawsuit successful the existent outbreak, the deadly influenza microorganism is inactive here.

"Generally, erstwhile the upwind gets hot, influenza goes distant for the astir part," Hagerman says.

That was the lawsuit successful the 2014-2015 outbreak — which came erstwhile Hagerman worked astatine the U.S. Department of Agriculture's Animal and Plant Health Inspection Service, oregon APHIS.

"Bright sunshine and vigor kills the microorganism successful the environment," Hagerman says, describing however summertime upwind helped extremity the earlier outbreak.

"This clip we didn't spot that microorganism circulation going down to zero successful our chaotic vertebrate population" implicit the summer, Hagerman says. Instead, the microorganism benignant of simmered done the summertime months, she adds, "and past we get into the cooler, wetter months of the autumn and we spot a resurgence."

The agelong outbreak is discouraging, Hagerman says: "If we look astatine Europe, we tin spot that they are connected 2 years of HPAI outbreaks."