I know my immune system will not let me die if I get some nasty germs in my system. But the way it protects me from dying is to propel the germs out of my body, possibly urgently, out either one end or the other. And I just can’t think of any time that is a “good time” to get sick and be either projectilely vomiting or having explosive diarrhea. Not to mention a major desire simply not to go through that.
So it’s not so much that I fear germs, it’s more that I fear losing time and going through unpleasantness by being sick. I’m a “sickophobe.”