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.
