Actually, seebs, there is just as much, if not more evidence in favor of the evil spirit theory of disease as there is in favor of the germ theory.
It is just your a-priori naturalistic bias that prevents you from considering the evil spirit theory as an option. If scientists were to admit that the evil spirit theory had merit, then they would have to acknowledge the role of God in curing disease. Because their whole careers are tied up in peddling naturalistic cures, the scientific establishment squashes any attempt to get the evil spirit theory taught in our medical schools.
In fact, the germ theory is just an INTERPRETATION of the evidence. Since no one has actually seen a germ causing disease doesn't, the germ theory is just that: a theory. Scientists just ASSUME that the germs cause the disease because they just happen to be found where the disease is most active. My theory, and this makes a lot of sense to me, is that it is the disease that causes the germs, not the other way around.
In reality it is just your spiritual blindness that prevents you from seeing that the evil spirit theory is an equally valid and equally scientific theory. The germ theory is yet another just-so Barney story that the secular humanists are using to promote their atheistic world view.