Highly pathogenic avian influenza has spread widely across North America this year, as this Oct. 16 map shows. Most of the cases in wild and domestic birds have been in the northern United States.
Highly pathogenic avian influenza has spread widely across North America this year, as this Oct. 16 map shows. Most of the cases in wild and domestic birds have been in the northern United States.
The avian influenza outbreak of 2022 will soon become the deadliest in recorded U.S. history.
As of Monday, some 50.3 million birds had been lost, approaching the 50.5 million that died in the 2014-15 outbreak.
This year’s outbreak was already the most widespread, with 619 premises infected, adding to the case that this is the worst avian influenza outbreak the nation has ever seen.
At the same time, there are signs that the U.S. has improved its performance against the disease since the last outbreak. That’s important because the threat of avian influenza isn’t going away any time soon.
This outbreak has affected all sectors of the poultry industry, but not equally.
By Nov. 8, when the death toll was just under 50 million, the U.S. had lost nearly 39 million laying hens, 8 million turkeys, 2.6 million broilers, 270,000 ducks and 117,000 backyard birds.
Most of the birds were killed not by disease but by humans wiping out the poultry on infected farms. In countries that can afford it, depopulation is used to prevent the disease from gaining a foothold and sickening birds on other farms.
The massive death toll for layers — three-quarters of the birds lost — came from just 32 farms, or 5% of infected premises. Egg farms have the largest average flock size of any poultry production system, over 1 million birds among the infected farms.
By contrast, 346 infected premises were backyard flocks — pastured and small-scale farms raising birds for sale, as well as coops that homeowners keep for personal use.
Because of their small flock sizes, backyard flocks accounted for just 0.2% of bird deaths despite being almost 60% of the infected premises.
The explosion of backyard cases is a departure from 2015, when only 21 such flocks were infected. That increase could be a result of the unusual virulence of today’s virus strain.
Most avian influenza strains start out comparatively mild, living in wild waterfowl. After the disease jumps from wild birds to poultry — via a gap in the poultry house or tracked-in feces — the virus can mutate to cause more severe illness and death.
That’s what happened in 2015, when the last major wave of highly pathogenic bird flu hit the U.S.
This year, though, the Eurasian H5N1 strain is starting out in waterfowl as infectious as the already-mutated disease from seven years ago. The current strain is even killing wild birds, which don’t usually show symptoms of avian influenza, said Mary Pantin-Jackwood, a USDA veterinary researcher, at a Maryland conference last month.
This year’s avian influenza death toll of 50 million has an equal only in the 2015 outbreak.
Since the first recorded highly pathogenic outbreaks in the 1920s, the disease has mainly surfaced in a single flock here or there.
The only other large outbreak, in 1983-84, killed 17 million birds, mostly in Pennsylvania.
The death toll from the two earliest documented outbreaks is unknown, but they were limited to East Coast live bird markets in 1924 and to New Jersey in 1927.
In fact, all of the outbreaks until this year were focused in one region of the country. In 2015, most of the 232 infected premises were in Iowa and Minnesota.
This year’s outbreak, with two and a half times more infected premises, is essentially nationwide, hitting 46 states and all four of North America’s migratory bird flyways.
With such an infectious strain on the loose, things arguably could have been worse.
Experts say the nation’s avian influenza response has been fine-tuned since 2015. Depopulation has been sped up. Indemnity payments to farmers have been streamlined. Other countries have agreed to limit the geographic scope of trade restrictions.
Indeed, by one measure of efficiency — the monetary cost of response — the current outbreak is not worse than 2015.
The USDA Animal and Plant Health Inspection Service has so far committed $567 million to fighting the current outbreak, compared to more than $850 million in 2015. USDA has described the earlier outbreak as the costliest animal health disaster in the nation’s history.
This year’s costs are $348 million to indemnify farmers for birds and eggs that were destroyed; $119 million for depopulation, disposal and virus elimination; and $100 million for personnel, state agreements and related costs, said Mike Stepien, a USDA spokesman.
It’s also notable that the U.S. has taken longer to reach 50 million bird deaths than it did in 2015. The previous outbreak was over in six months, while the current one has taken nine months to reach the same grim milestone.
A major reason for the slower overall deaths is faster deaths on infected farms.
This year’s focus on rapid depopulation has prevented the virus from multiplying in sick birds. Low virus loads, in turn, have minimized farm-to-farm transmission, which was a problem in 2015, said Julie Gauthier, assistant director for poultry health at USDA Veterinary Services, at a meeting last month.
Still, not every poultry-producing region of the country has been affected equally.
As in 2015, the Midwest has been brutalized. Pennsylvania, untouched in 2015, has had 34 outbreaks. Other hot spots have formed in the Delmarva peninsula, Utah, central California and the Canadian province of Alberta.
Meanwhile, the Deep South has been largely unscathed. Alabama and Louisiana have reported no cases in domestic birds, and Georgia has flagged just two backyard flocks. Mississippi only confirmed its first infected farm on Nov. 5.
It’s not that this region lacks poultry — it’s home to several leading broiler states — or that the South lacks wetland habitat.
In Alabama’s case, the state simply lies between the main routes of the Atlantic and Mississippi flyways, so fewer birds migrate through the state than through its neighbors, said Ken Macklin, a poultry science professor at Auburn University.
Even with good biosecurity, the amount of time birds spend on a farm may also be a risk factor, Macklin said.
Broilers, the South’s specialty, average just six weeks in a house. Turkeys and laying hens, with production centered in the North, stay in place weeks or months more.
“The longer the birds are in the poultry house, the more likely a breakdown in biosecurity will happen,” Macklin said.
The South may also have benefited from good timing — so far.
Macklin suspects avian influenza wasn’t so prevalent among wild birds when they flew north this spring, but they may have since spread it among themselves and passed it to waterfowl that live in the U.S. year-round.
As birds migrate south this fall, then, they could be carrying a bigger supply of the virus than they had in the spring.
“This winter I believe we will have multiple cases of HPAI in the Southern states,” Macklin said, pointing to the recent farm detection in Mississippi and three flocks of vultures that have tested positive in Alabama.
HPAI stands for highly pathogenic avian influenza.
The current outbreak is historic not just by American standards.
Europe has been dealing with an avian influenza epidemic of its own — the largest in the continent’s history, according to the European Centre for Disease Prevention and Control.
By Oct. 3, 48 million birds had been killed across almost 2,500 farms. As in the U.S., the disease has had an unprecedented geographic sweep, hitting 37 countries from Portugal to Ukraine to Norwegian islands north of the Arctic Circle.
Earlier this month, England required all poultry and captive birds to be kept indoors following an increase in avian influenza cases there.
Globally, 145 outbreaks involving 7 million commercial poultry were reported in 14 countries from September to mid-October.
Most of the cases were in beleaguered North America and Europe, though Algeria, South Africa and Taiwan were also affected, according to the World Organisation for Animal Health.
The agency also said the virus had persisted better in wild birds over the summer than it was ever known to before.
Europe’s experience also shows that avian influenza can, in rare instances, cross another type of border — from birds to humans.
Two poultry farm workers in Guadalajara, Spain, were infected with avian influenza this fall, though there is no evidence they spread it to other people, the World Health Organization said Nov. 3.
In the U.S., the Centers for Disease Control and Prevention has tracked the health of more than 5,000 people exposed to infected birds this year. Only one was found to be infected with avian flu, a depopulation worker from Colorado in April.
Avian influenza remains a low risk to the general public, with the concern being greatest for people who have prolonged exposure to sick birds and virus-contaminated surfaces.
The CDC says workers in such situations should wear protective gear like gloves and a mask, avoid touching their mouth or nose, and change clothes after handling birds.
Even after this outbreak ends — and it’s not clear when that will be — avian influenza will remain a threat to both humans and animals.
After all, four influenza pandemics have buffeted humans since 1918, and at least one, in 1968, involved a strain with genes from avian influenza, according to the CDC.
For all of the efficiencies of confinement poultry production, the system also puts thousands of birds at close quarters, allowing viruses to spread and mutate quickly, said Matthew Hayek, an assistant professor in New York University’s Department of Environmental Studies, in a recent paper.
Disease risk is also inherent in a globalized food supply chain that moves products quickly across great distances.
“It only takes one incident or error in the value chain, anywhere in the world, to cause a global outbreak,” a group of scientists wrote in a paper published this month by the Council for Agricultural Science and Technology.
To protect birds during the current outbreak, animal health officials are encouraging farmers to refuse unnecessary farm visitors, exclude other poultry owners from the farm, change clothes before and after entering the poultry house, and clean and disinfect footwear.
Sick or dead birds should be reported promptly to the state Ag Department. Phone numbers for reporting in the Mid-Atlantic states can be found here.
2022 is the worst year for highly pathogenic avian influenza since 2015. Lancaster Farming is tracking outbreaks, providing management informa…
A key reason is the virus dose needed to cause infection is much lower than in 2015, a USDA researcher says.
As the avian influenza outbreak begins to wind down, State Veterinarian Kevin Brightbill is reflecting on how Pennsylvania fared, and looking into how to handle future animal diseases.
The 2015 outbreak drove the U.S. to improve its animal disease preparedness, and it offers some insights for avoiding a repeat of that grim spring.
A market in Queens tested positive and has been depopulated. New York’s live bird markets once had long-running problems with avian influenza but have made strides against the disease in the past 20 years.
This is Maryland’s first detection in a commercial flock since March. The control area extends into Pennsylvania.
Phil Gruber is the news editor at Lancaster Farming. He can be reached at 717-721-4427 or pgruber@lancasterfarming.com. Follow him @PhilLancFarming on Twitter.
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