Many people confuse influenza or flu with the common cold. Flu is an acute infection of the airway tract in the nose and throat that can sometimes spread down into the lungs. Flu in adults is the most frequent cause of acute respiratory illness. Flu, however, affects people of all ages. Children are among the groups most at risk for developing flu and its complications.
Flu season begins every year mainly in late fall and early winter and in a widespread fashion.
The peak season for the flu is from November through March. Type A is the most common. Types A and B are further divided into different subtypes based on the chemical structure of the virus. These subtypes are responsible for the outbreaks of flu. Influenza is highly contagious.