Influenza, more commonly called the flu, is a contagious disease that is accompanied by respiratory problems and fever. It is an uncomfortable illness that is usually not dangerous t otherwise healthy people. Two type of viruses cause influenza: B.
Each type encompasses several different strains that are named for the place where they were first indentified, for example, “Hong Kong Flu” and “Russian Flu.” These unusual characteristic about flu virus is that once one strain spreads throughout a population, the virus strain changes in structure. Therefore, it becomes a new strain carrying a new form of influenza. The antibodies, or protective substances, produced by the body to combat the virus no longer work against recurrence of that virus because the virus has taken on different qualities.