Seasonal Influenza is an acute infectious disease of the respiratory system. Easy to transmit, it is caused by influenza viruses A, B and C. Type A is the most dangerous, as it is affecting many mammals and birds, causes most diseases in man and the most likely to create an epidemic. Type B affects humans and birds, and may also cause outbreaks, while Type C only affects humans and does not cause epidemics. The influenza virus is known for its unique ability to cause explosive epidemics and pandemics of acute febrile respiratory illness in all age groups. Influenza epidemic, which occurs every year, causes numerous health, social and economic problems. It is primarily transmitted between people by droplets from the nose and throat of an infected person who sneezes or coughs. The transfer can also be achieved by direct and indirect contact with respiratory secretions. The incubation period of influenza is only 1 to 3 days. The disease occurs very rapidly and is accompanied by high fever and more prominent general symptoms. Influenza causes many complications, and they may have a fatal outcome or requiring hospitalization, especially in older people. Complications are usually transient in nature but may be affected, and other organs. The basic treatmentof Influenza is symptomatic, whilte the most effective method of protection against seasonal flu is vaccination. It is recommended for all persons at increased risk and those who do not want to get sick from the flu.