WASHINGTON (Reuters) - Researchers have found some of the changes that a flu virus needs to become a deadly pandemic strain, and said on Tuesday the H5N1 avian influenza virus has so far made only a few of them.
WASHINGTON (Reuters) - Researchers have found some of the changes that a flu virus needs to become a deadly pandemic strain, and said on Tuesday the H5N1 avian influenza virus has so far made only a few of them.
