[Epidemiological actualization of the avian influenza. New analysis of sanitary risk]

A review has been made of the present epidemics of Avian Influenza, which originated in the year 2003 in Southeast Asia, and expanded thereafter to 60 countries in three continents (Asia, Africa and Europe), with more than 3000 outbreaks and millions of affected poultry, and 80% mortality. Special emphasis is made on the genetic variability of the etiological agent, the Orthomyxovirus A H5N1, which may accumulate point mutations in several genes distributed in eight segments, and especially in the gene which encodes the hemagglutinin (HA). Stress is made in a recent mutation in the gene which encodes polymerase PB2, which determines the substitution of one amino acid, and is associated to the virulence of the virion, enabling it to adapt to the upper human respiratory tract and to replicate in this area. This mutation dangerously approaches the virus A H5N1 to a possible interhuman transmission and to become a pandemic virus, possibly in the near future. The present knowledge and the social structure would permit to content and control the pandemic state with the due speed and efficacy.