Discovery is worst case yet in US outbreak that has already led Wisconsin governor Scott Walker to authorize National Guard to help contain the disease

A lethal strain of bird flu has been discovered in a flock of millions of hens at an Iowa egg-laying facility. Iowa is the top egg-producing state in the US and Monday’s discovery represents the worst case so far in a national outbreak that had already prompted Wisconsin to declare a state of emergency.

The US Department of Agriculture (USDA) said the Iowa flock numbered 5.3 million birds while the company that operates the farm said it was 3.8 million. It was unclear why there was such a discrepancy.



Iowa was already among the 12 US states to have detected bird flu infections since the beginning of the year. The other states with infected poultry flocks are Arkansas, Idaho, Kansas, Minnesota, Missouri, Montana, North Dakota, Oregon, South Dakota, Washington and Wisconsin.

Bird flu, also called avian influenza or AI, is a viral disease of birds. The US Centers for Disease Control and Prevention considers the risk for human infections to be low, and no human cases have so far been reported.



The latest discovery of infected birds was in a flock being raised near Harris, Iowa, by Sunrise Farms, an affiliate of the Sonstegard Foods Company, which sells eggs to food manufacturers, government agencies and retailers.

“We went to great lengths to prevent our birds from contracting AI, but despite our best efforts we now confirm many of our birds are testing positive,” Sonstegard said in a statement.

The flock has been quarantined and birds on the property will be culled to prevent the spread of the disease, the USDA said. The virus is deadly and can spread rapidly within an infected flock.

In Wisconsin, governor Scott Walker on Monday declared a state of emergency after a third poultry flock became infected within the past week, according to a statement from his office. The infected birds were chickens at an egg-laying facility, turkeys and a backyard flock of mixed-breed birds, comprising more than 326,000 birds in all.

Walker has authorized the state’s National Guard to help contain the disease, citing “thin” resources available from the federal government. The Guard will disinfect trucks exiting infected premises, a state spokeswoman said.

The USDA has spent $45m (£30.2m) so far responding to the US bird flu outbreak and has deployed about 60 people to Minnesota, the country’s top turkey-producing state, which has found more infected flocks than any other state.





