100 cold virus?
I you caught all the cold virus, wouldn't you be immuned?
Answers: Cold viruses mutate as they travel. Viruses are not living organisms, but to some extent proteins that raid cell and take them over to reproduce (kind of approaching aliens). Depending on the type of virus, sometimes when it takes over it doesnt be paid exact copies (the mutation part).
Also, you have to be suseptable contained by one way or another to obtain a cold, as if our body is able to quarrel it off, it will or may be milder contained by one person than another.
Problem near any virus is it mutates from time to time, and sometimes, person to character. With all the tentative bugs showing up all the time, you would never know how to gain that degree of imperviousness. Actually, yes. That is why older empire seldom get colds. They are immune to abundant of the viruses they caught when they be younger.