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Deadly Bird Flu Flew Over From Asia, Experts Say

Image: Indian health workers wring the necks of chickens during a culling

Indian health workers wring the necks of chickens during a culling operation at Venkateshwara Hatcheries in Thoroor village, India on April 14. Five chicks were found to be infected with H5N1 avian influenza on regular testing of samples belonging to the farm of a poultry farmer Srinivas Reddy. The authorities ordered the culling of 150,000 birds in a kilometer radius on poultry farms. NOAH SEELAM / AFP - Getty Images

The H5N2 virus that’s spreading among poultry is a new mutant, probably descended from a different virus called H5N8 that’s been plaguing poultry production in Europe and Asia for years, U.S Agriculture Department officials say.

They’re urging producers to protect their flocks by sweeping up spilled feed that might attract wild ducks, by disinfecting boots and equipment between poultry houses and even by watching for dust blown in that might carry infectious virus.

Bird flu viruses can spread quickly from one farm to the next, even with strict security measures. It’ll be important to double down as H5N2 has hit more than a dozen states, most recently forcing the destruction of more than 5 million laying hens at an Iowa farm, says USDA’s Chief Veterinary Officer Dr. John Clifford.

“This is very devastating to individual producers,” Clifford told NBC News.

“We have good biosecurity in this country, but I think we are dealing with something that is a little bit different now than we have in the past,” Clifford added. “We are going to have to change some things.”

“We are going to have to change some things.”

Producers are motivated — exports have already fallen, even though just a few million birds have been affected so far out of billions slaughtered every year.

Clifford said some farms are already implementing measures used in Europe, such as disinfecting boots as workers move from one poultry house to another on the same farm.

USDA has been working on a vaccine, but years of vaccinating birds has shown that immunizations are just one tool to use against bird flu. Flu viruses mutate, and it can be expensive and time-consuming to vaccinate multiple broods of poultry every year.

Genetic sequencing shows this virus, which just appeared in the U.S. at the end of last year, is a descendant of H5N8 viruses that have been wiping out and forcing the slaughter of poultry for decades.

Large outbreaks have been reported from Taiwan to Ireland. South Korea alone reported 65 outbreaks of H5N8 last fall.

The best guess is that migrating ducks or geese carried the virus across the Pacific to the west coast of North America. It’s affected flocks of chickens and turkeys, and been seen in a few individual wild birds, in a dozen states from Arkansas to Minnesota and in Canada.

It’s not clear how it is spreading from farm to farm in the U.S.

“Waterfowl can spread this virus,” says Clifford. Flu viruses can spread in bird droppings, and it’s possible that the ducks have landed on stocks of feed grain, says Clifford. Some of the affected farms are near lakes that could attract ducks, as well.

Wild ducks can and do carry bird flu, and U.S. Geological Survey scientists have been reporting infections in birds killed by hunters.

Bird flu hits Iowa flock hard 2:41

Corn not properly protected would attract wild waterfowl. That means poultry producers have to do much more than they usually do to protect feed from wild birds — covering up feed as it's moved and stored.

Wind might even blow contaminated soil onto feed, Clifford said. “It can blow dust and dirt or feathers across fields,” he said. “I am not saying that it did happen but I am saying these are all possibilities. We need to look at multiple ways of introduction.”

“Waterfowl can spread this virus."

One thing experts agree on is that this particular virus is not a threat to people. Two other strains of avian influenza — H5N1 and H7N9 — can infect people.

H5N1 has killed or forced the destruction of hundreds of millions of chickens around the world. It’s infected about 800 people and killed half of them — and the fear is it will mutate into a form that makes it pass easily from person to person. That would spark a pandemic that could kill millions.

H7N9 has a similar ability to cause a pandemic. It’s infected more than 600 people in two years and killed about a third of them.