Q&A: Details about what's next in bird flu response efforts

More than 414,000 turkeys and chickens have been killed, some through a method considered a "last resort" of euthanasia, at 10 southwest Indiana farms affected by a bird flu outbreak. Testing and monitoring will continue for weeks to determine if the outbreak of the H7N8 viral strain is contained. That strain is different from one that led to the deaths of more than 48 million birds last summer.

Here are some questions and answers about what happened and what's next in the response to the outbreak in Dubois County, Indiana's top turkey-producing county about 70 miles west of Louisville, Kentucky:

WHEN WERE THE LAST BIRD FLU CASES CONFIRMED?

Indiana's last bird flu cases were confirmed Jan. 16. Animal health officials announced the previous day that a form of the viral strain that was causing infected birds to die had been found at a turkey farm in Dubois County. The next day, officials said the virus had been detected at nine other turkey farms. Eight of those farms had a form of the viral strain that only made the birds sick; testing continues on the virus found at the ninth farm.

HOW MANY BIRDS WERE EUTHANIZED?

Crews on Wednesday finished euthanizing more than 258,000 turkeys at the 10 affected farms and more than 156,000 egg-laying chickens at one of those 10 farms. Those chickens did not have the virus, but officials said they were at high risk of infection due to their close proximity to a barn with infected turkeys.

WHAT HAPPENED TO THE BIRDS AFTER THEY WERE EUTHANIZED:

All of the birds' carcasses remain in the barns where they were killed and are undergoing a type of composting in which they are placed in piles with organic material and heated so the remains will decompose. That method destroys the virus. Experts in the monthlong composting process are now supervising those efforts.

WHAT ELSE IS BEING DONE TO ENSURE THE VIRUS DOESN'T SPREAD?

Testing and surveillance of commercial poultry farms is ongoing in a 12.4-mile radius around the first turkey farm where the virus was detected. That radius extends beyond Dubois County into four adjacent counties. As of Friday, 124 commercial poultry farms within that response area had been tested at least once and no viral cases had been found. Each will soon undergo a second round of testing.

IS TESTING BEING DONE ON BACKYARD POULTRY FLOCKS?

Officials are going door to door within a 6.2-mile control zone around the first turkey farm where the virus was found to ask residents if they have backyard poultry flocks. Ninety-six such flocks have been found. Seventy-six of them have been tested so far, with no virus found. Testing is continuing on the other flocks. All 96 flocks will be tested every seven days until each passes three times.

HOW WERE THE BIRDS IN THE OUTBREAK EUTHANIZED?

Some of the turkeys were suffocated by being covered in a liquid foam or by carbon dioxide that was pumped into their barns, and some were killed manually. All 156,000 chickens were suffocated by switching off barns' ventilation systems and turning up the heat inside. Some turkeys also died after their barns' ventilation systems were turned off and the heat was increased inside.

WHICH AGENCY AUTHORIZED TURNING OFF THOSE VENTILATION SYSTEMS?

Animal rights activists have decried as cruel the euthanization method of turning off poultry barns' ventilation systems and raising the heat inside to suffocate birds. Indiana's state veterinarian, Dr. Bret Marsh, said the U.S. Department of Agriculture authorized the immediate closure of ventilation systems at all 10 affected turkey farms.

WHY WAS THAT EUTHANISIA METHOD ALLOWED?

Marsh said the USDA allowed that step at all 10 farms in response to concerns that the virus could become airborne and spread to adjacent farms in poultry-intense Dubois County. In some barns, the heat was also turned up, suffocating some turkeys. The USDA considers that a "last resort" method to kill infected poultry. Marsh said the USDA permitted those steps because the virus was found simultaneously at so many farms that the time needed to arrange other euthanization methods would have raised the risk of the virus spreading.