Bird flu has been detected in a US turkey flock but is different from the strain that devastated the nation's poultry industry last year, officials said Friday.

Nearly 50 million birds were killed or destroyed after bird flu swept across the United States in 2015, infecting 211 commercial flocks in 15 US states from California to Indiana.

The current highly pathogenic strain -- H7N8 -- was detected after testing turkeys from an Indiana flock that "experienced increased mortality," the US Department of Agriculture said.

"State officials quarantined the affected premises and depopulation of birds on the premises has already begun," the USDA said in a statement.

"Birds from the flock will not enter the food system."

There are no known cases of bird flu infection in humans, the USDA said, adding that proper handling and cooking of poultry and eggs will kill bacteria and viruses like the bird flu.

Avian influenza is typically spread by free-flying waterfowl like ducks, geese and shorebirds.