Influenza viruses with pandemic potential and measures to prevent their emergence

Based on the analysis of current data presented in scientific publications five main theses on emergence of influenza viruses with pandemic potential were stated and additional measures to prevent their appearance were suggested. Three groups of viruses were considered: 1) previous pandemic viruses being reassor- tant/recombinant viruses of humans and animals; 2) new reassortants of human and animal influenza viruses supposed to appear in circulation; 3) influenza viruses of animal origin. According to the authors’ opinion each of these three groups may generate pandemically actual viruses under certain conditions. Viruses representing the second group seem to be the most dangerous agents capable to emerge as shift-variants due to successive number of events: combination of human influenza epidemic outbreaks with animal influenza epizootics; concurrent reproduction of two different related viruses in the same cells during mixed influenza infection in humans or animals; series of further obligatory consecutive passages of pathogenic reassortant viruses in human population. The refore interruption of epidemic interaction in the system «human-animal» should be the goal of prophylactic measures. Priority of regular vaccination with inactivated influenza vaccine for human groups at high professional risk of influenza transmission from animals (swine, birds) is recommended additionally to the protection available in current practice. Urgent influenza chemoprophylaxis for humans being in contact with persons infected with animal influenza viruses or a supposed viral reassortant is also recommended.