Hong Kong, CHINA: Captive birds for sale are contained in a cage at a bird market in Hong Kong, 08 March 2007. Researchers in the United States believe they have found an easily-produced vaccine for the killer H5N1 bird flu that could halt a feared pandemic, a media report said 05 March. AFP PHOTO/TENGKU BAHAR (Photo credit should read TENGKU BAHAR/AFP/Getty Images)