Influenza or seasonal flu is an illness that is very common and appears every year specially during the winter months. It is a highly infectious condition caused by the flu virus, which generally affects your lungs and upper airways. 

The infection leads you to develop a sudden high temperature often aided by body aches. Some individuals also tend to lose their appetite, feel nauseous and have a dry cough during the infection.

The virus affects a huge number of people every year through out the different parts of the world. It is common to find flu as a reason of absence from work or school. Most individuals don't consult their doctors when they catch flu, in spite of that there are about 50 and 200 for every 100,000 people who contact their doctors.

There are several strains of the flu virus that can circulate at the same time. In the year 2010-11, H1N1 was one of the season's strain that caused the swine flu. The flu virus is capable of forming new strains over a period of time which makes it all the more difficult to avoid it the second time even if you had flu once.