The threat of avian influenza A (H5N1). Part I: Epidemiologic concerns and virulence determinants.

Among emerging and re-emerging infectious diseases, influenza constitutes one of the major threats to mankind. In this review series epidemiologic, virologic and pathologic concerns raised by infections of humans with avian influenza virus A/H5N1 are discussed. This first part concentrates on epidemiologic concerns and virulence determinants. H5N1 spread over the world and caused a series of fowl pest outbreaks. Significant human-to-human transmissions have not been observed yet. Mutations that make the virus more compatible with human-to-human transmission may occur at any time. Nevertheless, no one can currently predict with certainty whether H5N1 will become a human pandemic virus.