The threat of avian influenza a (H5N1): part II: Clues to pathogenicity and pathology.

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. The second part focuses on experimental and clinical results, which give insights in the pathogenic mechanisms of H5N1 infection in humans. H5N1 is poorly transmitted to humans. However, H5N1-induced disease is very severe. More information on the role entry barriers, H5N1 target cells and on H5N1-induced modulation of the host immune response is needed to learn more about the determinants of H5N1 pathogenicity.