Abstract
Influenza viruses undergo evolution by the shift (influenza A viruses) and the drift of envelope glycoproteins. Since predicting the direction of the antigenic evolution of influenza viruses is impossible, it is necessary to monitor wild viruses in nature. An important objective is to control the circulation of influenza viruses in natural reservoirs, interspecies transmission, especially the acquisition by avian influenza viruses and their ability to infect mammals, and detection of cases of stable transmissibility of such strains. In addition to antigenic evolution, it is necessary to identify and track the patterns of evolution of other biological properties of influenza viruses that might promote the evasion of viruses from the factors of nonspecific defense of the body and aggravate the epidemic process.
Keywords: Avian influenza, Evolutionary variability, Human influenza, Influenza virus, Nature reservoirs, Swine influenza.