Your comment seems to clearly show a complete misunderstanding of the workings of the human immune system and disease, not to mention a tenuous grasp on the rules of grammar in the English language.
Firstly, everyone does *not* continuously have the common cold. If that were the case, the immune system would be weakened such that it would be unable to effectively fight other disease. Your statement that a subject would die or nearly die if they were to not have the common cold is also invalid. In most humans (excluding patients with existing diseases, immune deficiencies, and genetic defects), the immune system does not have to "readjust" to combat a pathogen, assuming it is one that they have already been infected with, inoculated against, or infants, who are still protected by antibodies present in their mother's milk. Rather, the antibodies in their blood will instantly bond with the pathogens and direct the immune system to destroy them, without an adjustment period.
Next, your grammar skills leave something to be desired. For example, in the first sentence, because "everyone" is plural, "have" should be "has". Your post, corrected for grammatical (but not scientific) accuracy, should read more or less as follows:
"The amusing part is that EVERYONE has the common cold, it's just a matter of whether your immune system currently has it under control, or if it is currently flaring up. If you ever didn't have it you would notice getting it by almost dying, as it would take too long for your immune system to readjust."
Numerous websites can be found in a quick Google search on grammar rules, feel free to search for them at your leisure, as I do not feel like looking through them for the best one. The Wikipedia page on the immune system can be found here: http://en.wikipedia.org/wiki/Immune_system
The amusing part is that EVERYONE have the common cold.. it's just a matter of whether your immune system is currently having it under control, or if it is currently flaring up.. (If you ever didn't have it you would notice getting it by almost dying, as it would take too long time for your immune system to readjust)