What is Flu?

Flu, or influenza, is a specific infection of the upper respiratory tract caused by a group of viruses known as the influenza virus. The other common infection in this part of the body is the common cold – these are also caused by viruses and over 200 cold viruses have been described.

Symptoms of flu are similar to those of colds, but are usually more severe. Without the use of laboratory tests, it is usually not possible to tell if you have flu or a cold and people generally take the view that if their cold or flu symptoms are severe, they are suffering from flu.