Health officials have issued a global warning about a virulent flu and pneumonia that has swept through hospitals in Hong Kong and Vietnam.One man has died, dozens of hospital workers have fallen ill, and some of these are reportedly in a critical condition. The precise origin of the infection is still unknown, but the key case involved an American businessman who died on Thursday morning in a Hong Kong hospital. He had arrived into Hanoi in Vietnam from Shanghai on a business trip already suffering from severe respiratory problems. When his condition deteriorated, he was transferred to Hong Kong for...