Recognition of the Influenza A Virus

H antigen and N antigen of influenza virus are easy to occur variation,mainly in the influenza A virus.Influenza A3 viruses have been isolated in secretions of children with acute tract infection from Beijing,Guangzou and Tianjin.The avian influenza virus maybe form a new type of reassortment strains through variation of antigens or gene reassortment with human influenza virus.Thus,it has possessed ability of person to person transmission.Once continuous variation occurred in hemagglutinin and N antigen,the reassortment influenza virus strains will evade recognition and clearance from human immunological system,and thus cause a new prevalence because it is able to break through the immunobarrier of population repeatedly and effectively.