How To Tell If Someone Has The Flu

The flu is a contagious viral infection of the respiratory tract. It is, perhaps, the most common illness seen throughout the winter, aside from the common cold at least. The flu is caused by an influenza virus (the exact strain or strains vary from year to year) and the symptoms can be mild to severe. Symptoms typically commence two days after exposure to the virus and most last less than a week, although the cough may last for more than two weeks.