An outbreak of a highly pathogenic avian influenza strain is decimating wild and farmed bird populations globally, fueling a debate about the most effective ways to end it and the potential risk to humans.
Some experts are concerned about the possibility that the H5N1 virus could one day evolve to more easily spread from birds to mammals. Although the risk to humans remains low, speculation about the virus has caused worry that the bird flu outbreak could develop into a larger threat.