The newer strain had been seen before in more than a dozen people exposed to poultry, but this is the first time an infection was traced to a cow. The Nevada dairy worker was exposed at a farm in Churchill County, in the west central part of the state, state health officials said.

Nevada has confirmed its first human case of bird flu in a farm worker who was exposed to infected dairy cattle, the Central Nevada Health District said on Monday, after authorities last week reported a second strain of the virus in cows in the state.