Bird flu continues to spread across the state prompting Nebraska agriculture officials to ban all auctions and fair events involving poultry. The Nebraska Agriculture Department announced Saturday that a fourth case of avian influenza had been confirmed in the state although this latest one came in a small backyard flock in Holt County instead of a large commercial operation. Cases of the highly contagious disease have been confirmed in at least 18 states, and more than 13 million chickens and turkeys have been slaughtered to limit its spread. Health officials have said the disease doesn't present an immediate public health concern to humans.