How does the human body respond to flu?

Answer 1

When the immune system in your body detects the flu virus it directs a particular type of white blood cell toward the virus called a macrophage. This white blood cell swallows up the virus and breaks it down into small parts. These small parts are then presented to other types of white blood cell known as T-cells which produce chemicals that tell your body that it is under attack by the virus. One of the responses to this is the production of antibodies which help your immune system seek out and destroy other copies of the virus, they are also stored so that if you are infected by the same (or a very similar) flu virus again your body can respond faster before the virus takes hold.

It is the chemicals made by T-cells which make you feel ill. They are very toxic which is good for killing viruses but unfortunately also causes a high temperature, muscle aches, headaches, nausea, tiredness and all the other symptoms associated with flu. So really the sickness we see when someone has flu is actually part of the body's plan to destroy the virus before it infects all the cells in your body. It is a balance between killing the virus and killing you!