Officials confirmed an outbreak of highly pathogenic avian influenza at the end of last week after abnormal mortality was noted in a turkey flock. Nine other premises have since been found to be infected with a low pathogenic form of the disease.

An update from Indiana State Board of Animal Heath (BOAH) on 19 January said that state and federal teams had visited 1248 residences in a 10-kilometre radius control zone around the original site to search for small, backyard flocks of birds for precautionary monitoring and testing.

The update said a total of 46 backyard flocks have been found, and sampling is in progress.

An extension of an extra 10-kilometre "surveillance zone," beyond the 10-km control zone, has also been put in place as a precaution.

Birds have been humanely euthanised on seven premises, with another three premises currently underway, the report said. Depopulation efforts were initially hampered by extremely cold temperatures, which froze water sources.

The depopulated turkeys will be composted in the buildings in which they were euthanised. The composting process takes about three weeks, after which time, the compost can be used agriculturally because it will not contain the virus.

An additional 155,000 hens (chickens) that are not infected with H7N8 have been depopulated and disposed of in a landfill. The building shares a vehicular traffic zone with the original site. No chickens are infected.

The total number of birds affected, which will eventually be depopulated, is 401,163.