The seasonal flu is an infectious disease caused by RNA viruses of the family Orthomyxoviridae (the influenza viruses) that affects birds and mammals. The name influenza comes from the Italian influenza, meaning “influence” (Latin: influentia). Influenza is a viral infectious disease that is considered one of the most important causes of respiratory tract infections. Symptoms are similar to those of the common cold, however, are more severe, and their beginning is generally abrupt. Influenza can affect a significant number of persons of all age groups during the occurrence of an epidemic. This disease frequently requires medical attention and hospitalization, contributing significantly to economical losses, excessive numbers of hospitalizations, and deaths. The ability of influenza A and B viruses to suffer gradual antigenic changes in their ...