EVART, Mich. (AP) — Alison Smith stared at the virtually empty dairy barn inside the Osceola County Fairgrounds, once bustling with teens and preteens preparing to show their prized animals but now eerily silent as an invisible virus once again interfered with a cherished summertime rite. Smith, a 16-year-old from the Grand Rapids, Michigan, area, had invested a significant amount of time over the past year preparing two heifers, Evergreen and Perfect, for competition at the fair. But like hundreds of fairs nationwide, a recent bird flu outbreak, now spreading among mammals, forced significant changes — or outright cancellations — of the livestock contests that are a hallmark of summer fairs.