Bird flu viruses diversifying, making vaccine target harder to pick: WHO 19:23:04 EDT Aug 18, 2006 Canadian Press: HELEN BRANSWELL, The Canadian Press (CP) - The World Health Organization urged influenza vaccine makers Friday to use newer strains of virus when making vaccine to protect against H5N1 avian flu, saying the evolution of the microbe has led to increased variety in circulating strains. While the diversity creates challenges for vaccine manufacturers - and potentially additional costs for the governments paying them to make and test vaccine against H5N1 - it does not mean the worrisome virus has moved closer to...