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Researchers discover H5N1 is far more dangerous than previously believed. "In the past, outbreaks of highly pathogenic avian influenza in poultry began following the primary introduction of a virus, of low pathogenicity, probably carried by a wild bird. The virus then required several months of circulation in domestic poultry in order to mutate from a form causing very mild disease to a form causing highly pathogenic disease, with a mortality approaching 100%. Only viruses of the H5 and H7 subtypes are capable of mutating to cause highly pathogenic disease. In the present outbreaks, however, asymptomatic domestic ducks can directly introduce the virus, in its highly pathogenic form, to poultry flocks." Limiting this conclusion to domestic
waterfowl proved to be wishful thinking, as in later months it became clear that nondomestic
waterfowl were also directly spreading the highly pathogenic strain of H5N1 to
chickens,
crows,
pigeons, and other birds and that it was increasing its ability to infect mammals as well. From this point on,
avian influenza experts increasingly refer to containment as a strategy that can delay but not prevent a future avian flu pandemic. == November ==