A review and update about a new zoonosis, as it is the Avian Influenza or "poultry grippe" has been made. This disease is endemic in the Southeast of Asia and continues at present time, being active in Vietnam and Tailand. We have considered the Natural History of the Avian Influenza and specifically the late epidemies, starting from the one in 1997 in Hong Kong, in which an Orthomyxovirus type A, subtype H5N1, broke the interespecies barrier. A health analysis is made, both for the present moment and the future, about the possibility of a World pandemic flu, originated by the mentioned Orthomyxovirus type A, agent of the Avian Influenza of highly virulent specificic virus strain pathogenic for men. The most favourable fact, among others, to deny the possibility of a future pandemic flu is the stability of H5N1 strain in both epidemics of poultry in Hong Kong and in the Southeast of Asia.