Influenza is a viral infection, wich affects mainly the throat, nose, bronchi and lungs. Infection usually lasts for about 6-7 days, and is characterized by onset of high fever, aching muscles, headache and severe malaise, cough and sore throat. The virus is transmitted from person to person via droplets and small particles produced when infected people cough or sneeze. Influenza spreads rapidly in seasonal epidemics. Most infected people recover within one or two weeks without requiring medical treatment. However, in the children, the elderly, and those with other serious illness, infection may lead to severe complications of the underlying condition, pneumonia and even death.