BIRD FLU VIRUSES DIVERSIFYING, MAKING VACCINE TARGET HARDER TO PICK: WHO

The World Health Organization urged influenza vaccine makers 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.

Yahoo Canada (http://ca.news.yahoo.com/s/18082006/2/xhealth-bird-flu-viruses-diversifying-making-vaccine-target-harder-pick.html)