Progresses on Studies of Highly Pathogenic Avian Influenza H5N1 Cross-Species Infection and its Pathogenesis

The threat posed by highly pathogenic avian influenza A (H5N1) viruses to humans remains significant since the virus has caused sporadic human infections in 16 countries with a high case fatality rate (approximately 60%), circulated in poultry in several countries, and has the potential possibility to induce pandemic by mutation or/and reassortment with other influenza A subtypes. Although many studies showed that a number of amino acid mutations may contribute the adaption, transmissibility or the pathogenicity of avian influenza A H5N1 virus in mammals, the mechanism of the cross-species transmission is not clear so far. The current evidences indicated that both the virus and infected host itself played key role on viral infection and the pathogenesis. Therefore, in addition to monitoring the virus activity and molecular changes, discovery on the pathway of host regulation and control linked to viral infection factors would be also very helpful to control and prevent the disease.