CHICAGO (Reuters) - Minnesota, the top U.S. turkey producing state, has found two more commercial turkey flocks to be infected with a lethal strain of avian flu, including one in a previously established quarantine zone, the U.S. Department of Agriculture said on Monday.
The state in the past month has found that H5N2 flu, which can kill nearly all the birds in a flock within 48 hours, has infected seven flocks, according to the USDA. In the last week alone, the number of birds to be culled in Minnesota because of the flu has topped 150,000.
The infected flocks were in the state's biggest turkey-producing counties. Kandiyohi and Stearns counties were the top two turkey-producing countries in Minnesota in 2012, according to the Minnesota Turkey Growers Association.
Minnesota's turkey farmers raise about 46 million birds annually accounting for more than $600 million in income, according to association. Nationwide, farmers raised about 240 million turkeys in 2013, according to the USDA.
Ninety percent of the turkey products processed in state are exported out of Minnesota, and of that 90 percent, 15 percent are exported, the association said.
Recent bird flu infections in states stretching from Arkansas to California have prompted overseas buyers to limit imports of U.S. poultry from companies such as Tyson Foods Inc, Pilgrim's Pride Corp and Sanderson Farms Inc.
The latest U.S. infection was the third case detected in Stearns County, Minn., which is northwest of Minneapolis. The infected flock of 76,000 turkeys is already in a quarantine zone established because of a previous infection in the county, according to the USDA. The quarantine limits the movement of poultry in and out of the area around an infected flock.
Another new case of H5N2 flu was detected in a flock of 26,000 turkeys in Kandiyohi County, Minn., which is west of Minneapolis.
Both flocks will be culled to prevent the virus from spreading, and the birds will not enter the food supply, according to the USDA.
Officials believe the flu is likely being spread by waterfowl, but do not know precisely how the virus is making its way into commercial poultry operations. Molecular testing has shown the H5N2 virus is nearly identical to viruses isolated in migratory ducks, according to the USDA.
Wild birds can carry the disease without appearing sick, and the USDA has advised people to avoid contact with sick or dead poultry and wildlife.
So far, no human infections of the virus have been detected.
(Reporting by Tom Polansek; Editing by Alden Bentley and Bernard Orr)