MARCH 01, 2006

The identification of 4 different strains of H5N1 (the avian flu virus) in southeast Asia has implications for preparation to ward off a possible pandemic and the vaccines that may be needed to protect against human infection, according to the results of a study reported recently in the Proceedings of the National Academy of Sciences.

Researchers have discovered that the H5N1 virus exists commonly in domesticated poultry populations and also in wild birds before they migrate. Using genetic analysis, the investigators identified 4 sublineages of the virus existing in birds from different geographical areas. Whereas H5N1 can be spread over long distances in migratory birds, in southeast Asia infected poultry seem to be the main way the virus is transmitted. Better surveillance of bird populations to ensure that one of the H5N1 variants does not begin to spread more easily between individuals is a key recommendation, noted the researchers.

Lead researcher and flu expert Robert Webster, PhD, said that the findings underscore the need for a variety of vaccines. "Multiple, different vaccines are going to have to be prepared and held ready in case one of these goes human-tohuman," he said.