Influenza more well known as the flu is a contagious respiratory illness which caused by influenza virus. When contracted following symptoms can occur such fever coughs sore throats body aches fatigue and chills. The flu usually spreads via indirect contact with droplets from infected person's mouth you contract it when someone coughs on or to surface touch. common in colder seasons of year. On some occasions especially those weakened immune systems (elderly people young children) other illnesses emerge pneumonia