(Radio Iowa) – Bird flu is confirmed at a third dairy in northwest Iowa as state and federal officials are trying to find out how the virus spreads between farms and livestock. On Wednesday, Iowa’s ag department confirmed avian influenza at a dairy farm with 17-hundred cows in Sioux County. State veterinarian Jeff Kaisand says most cows recover within a few weeks, unlike infected poultry, which are euthanized.

“We do have a USDA epi strike team that’s on the ground in Iowa right now that we requested,” Kaisand says. “They’re trying to help us understand some of those connections between farms to try and reveal some of those connections as best we can.” It’s the second case in Sioux County and the third in the state after the virus was first found in an Iowa dairy in O’Brien County last week. Kaisand says one priority is trying to figure out how avian influenza spreads between farms and livestock.

“We don’t know how it moves through the whole herd,” he says. “Does it go through all at once, or are there pockets that it doesn’t go through? And also trying to understand how it goes through a dairy herd or a poultry herd or vice versa.”

The Department of Agriculture and Land Stewardship recently started testing dairies within a 12-mile radius of infected poultry farms.