 The four positive results were found after about 60 people from the poultry farm were symptomatic and tested. Based on genetic sequencing, the hypothesis is that the virus spilled over from infected dairy cows into the poultry. Dr. Nirav Shah with the Centers for Disease Control and Prevention says workers were culling poultry in barns that were baking in the summer heat. This made it hard to wear personal protective equipment, plus they were using large fans. But those fans also spread things like feathers around, which are known to carry the virus.