How America lost control of the bird flu, setting the stage for another pandemic

Keith Poulsen’s jaw dropped when farmers showed him images on their cellphones at the World Dairy Expo in Wisconsin in October. A livestock veterinarian at the University of Wisconsin, Poulsen had seen sick cows before, with their noses dripping and udders slack.

​ Keith Poulsen’s jaw dropped when farmers showed him images on their cellphones at the World Dairy Expo in Wisconsin in October. A livestock veterinarian at the University of Wisconsin, Poulsen had seen sick cows before, with their noses dripping and udders slack. Read More Breaking News, Latest News and Videos | CNN