Why do we get sick?

Why is it that we are feeling fine and then all of a sudden we get run down and then come down with a terrible cold, cough, fever, etc...

When is the cold season? What is the times of year that different things go around? Why is it that we get more colds in the winter than in the summer and why does the flu only come around a certain time of year?

I have a few of these answers but it all just kind of stems from what is happening in the world around us! Like for instance the H1N1.... This started somewhere else during our "flu season" or just a little before it so we were prepared for the flu season and the season to be extra bad because it was going to include this extremely scary virus H1N1!

I have a theory on why we get sick in the winter more than the summer... Could it be because we stay in heated rooms all day long and then emerge into chilly temperatures to go out to dinner, the grocery store, etc. And if this is the case, why doesn't it effect people the other way around? Like durring the summer, we always have air condition going and then we step out into the blazing heat to get into a scorching car to blast the air in on us...

I think the winter is a bigger shock on our bodies though and our bodies work harder to keep us warmer, ultimately making us vulnerable to those pesky viruses waiting to infultrate our bodies and force us to rest!

Since I've left all these questions, here is another one to ponder... Why is it with sore throats that they hurt so much more in the morning and then lessen as the day goes on, well at least a little. And why is it that some people get sore throats and some don't, even though it's the same virus?

What are your thoughts??????????