UPDATE: Bird flu outbreak contained to 10 Indiana farms

No additional turkey farms in a southern Indiana county have tested positive for bird flu since an outbreak at 10 farms, where nearly 250,000 turkeys will be killed as a result, authorities said Sunday.

That 100 farms tested over 24 hours came back negative was a sign control measures appear to be working, said Denise Derrer, spokeswoman for the Indiana State Board of Animal Health.

She called the current bird flu outbreak one of the worst to ever strike Indiana, adding it could take several weeks before it is known for sure that it has been contained. The infections were reported Friday and Saturday.

All 60,000 turkeys at the first farm where the bird flu was detected have been euthanized. Not all the 250,000 had yet been killed, said Derrer, though she didn't have specific figures.

The initial farms are in Dubois County, about 70 miles from Louisville and 120 miles from Indianapolis. All of the infections were within a quarantine area set up around the first farm and that area was expanded to four neighboring Indiana counties — Martin, Orange, Crawford and Daviess.

Most of the additional tests were done within about a six-mile radius of the infected farms. But some producers tested farms outside that radius — a few even in Illinois near the Indiana border, Derrer said.

"They want to make sure it is not being spread," she said.

Derrer said Thursday morning that laboratories determined the strain of all ten infected farms in Dubois County was H7N8 — though she said later that additional tests were being done on one of those farms.

Confirmation of new bird flu cases alarmed industry officials after the spread of the H5N2 virus last year. That outbreak led to the deaths of about 48 million turkeys and chickens.

The H7N8 virus has not yet been found in wild birds, suggesting that the virus could have developed in wild birds that spent the winter in southern Indiana, USDA spokeswoman Andrea McNally said Friday.

While the H7N8 strain is highly contagious for birds, the USDA said no human infections from the viral strain have been detected.

Indiana's poultry industry brings in $2.5 billion a year, Derrer said, adding that the state leads the country in duck production, is No. 3 in egg production and fourth in turkeys. Dubois County is Indiana's top poultry producer with 1.4 million turkeys, she said.