AVIAN flu has reached new corners of the globe and become endemic for the first time in some wild birds that transmit the virus to poultry, according to veterinarians and disease experts.
They warn, it is now a year-round problem.
Experts say the prevalence of the virus in the wild signals that record outbreaks will not abate soon on poultry farms, ramping up threats to the world's food supply. They warn that farmers must view the disease as a serious risk all year, instead of focusing prevention efforts during spring migration seasons for wild birds.
Outbreaks of the virus have continued in North and South America, Europe, Asia and Africa, undefeated by summer heat or winter cold snaps, since a strain arrived in the United States in early 2022 that was genetically similar to cases in Europe and Asia.
Egg prices set records after the disease wiped out tens of millions of hens last year, putting a staple source of cheap protein out of reach of some of the world's poorest at a time the global economy is reeling from high inflation.
Wild birds are primarily responsible for spreading the virus. Waterfowl like ducks can carry the disease without dying and introduce it to poultry through contaminated faeces, saliva and other means.
Farmers' best efforts to protect flocks are falling short.
Rose Acre Farms, the US second-largest egg producer, lost about 1.5 million hens at a Guthrie County, Iowa, production site last year, even though anyone who entered barns was required to shower first to remove any trace of the virus, chief executive Marcus Rust said.
A company farm in Weld County, Colorado, was infected twice within about six months, killing more than three million chickens, Rust said. He thinks wind blew the virus in from nearby fields where geese defecated.
"Avian flu is occurring even in a new poultry farm with modern equipment and no windows, so all we could do now is ask God to avoid an outbreak," said Shigeo Inaba, who raises chickens for meat in Ibaraki prefecture near Tokyo.
"It's a new war," said Bret Marsh, the state veterinarian in the US state of Indiana.
Indiana lost more than 200,000 turkeys and other birds over the past year, and total US deaths top 58 million birds, surpassing the 2015 record.
The virus is usually deadly to poultry, and entire flocks are culled when even one bird tests positive. Vaccinations may reduce but not eliminate the threat from the virus. Still, Mexico and the EU are among those vaccinating or considering shots.
Wild birds have spread the disease farther and wider around the world than ever before, likely carrying record amounts of the virus, said Gregorio Torres, the head of the science department at the Paris-based World Organisation for Animal Health, an inter-governmental group and global authority on animal diseases.
The virus changed from previous outbreaks to a form that is probably more transmissible, he told Reuters. Torres could not confirm the virus is endemic in wild birds worldwide, though other experts said it is endemic in certain birds in places like the US.
The World Health Organisation says the risk to humans is low.
The form of the virus circulating is infecting a broader range of wild birds than previous versions, including those that do not migrate long distances, said David Suarez, acting laboratory director of the US government's Southeast Poultry Research Laboratory in Georgia.
Such infections of "resident" birds are helping the virus to persist throughout the year when it didn't previously, he said.
Black vultures, which inhabit the southern US and previously avoided infections, are now among the species suffering, said David Stallknecht, director of the Southeastern Cooperative Wildlife Disease Study at the University of Georgia.
The virus has also infected foxes, bears and seals.
High virus levels in birds like blue-winged teal, ducks that migrate long distances, helped spread the virus to new parts of South America, Stallknecht said.
Peru, Ecuador and Bolivia in recent months reported cases. Ecuador imposed a three-month animal-health emergency on Nov 29, two days after its first case was detected.
The writer is from the Reuters news agency