Why do you get a fever?

https://www.youtube.com/watch?v=F_W6F863uZA

In this video a man is explaining why do people get hot when they get a cold. The thing is that we are usually hot to prevent the virus and when we get wet or our body temperature decreases, the virus attack our immunological system. There are two types of virus that attack our system in winter : rhinovirus and adenovirus. So what he sais is that the solution for our physical discomfort is to staying home watching tv or taking easy , so we can get again hot.