KALAMAZOO, Mich.—A strain of highly pathogenic avian influenza has been detected in Michigan in a non-commercial backyard flock of birds in Kalamazoo County, federal authorities said Thursday. Samples from the flock were tested at Michigan State University’s Veterinary Diagnostic Laboratory and confirmed by the USDA’s Animal and Plant Health Inspection Service laboratories in Ames, Iowa. State officials have quarantined the Kalamazoo County site and the 34 birds at that property “will be depopulated to prevent the spread of disease,” the USDA said, noting that birds from that flock will not enter the food system. It’s the first case of avian flu in Michigan, said Lyndsay Cole, a USDA spokeswoman. It’s not clear how it reached the backyard flock, she said. The virus strain is potentially deadly to commercial poultry. The bird flu cases are among the latest in the United States that have put farms that raise turkeys and chickens …