A FUNCTIONAL APPROACH TO DISEASE
First, a functional classification of the signs and symptoms of disease is important and useful. In order to choose appropriate treatment, we need to know if the cough, or other symptom, benefits the patient or the pathogen. We also need to know if the pathogen is manipulating the host or attacking its defenses. Instead of just relieving symptoms and trying, perhaps inef- fectively, to kill the pathogen, we can analyze its strategies, try to oppose each of them, and try to assist the host in its efforts to over- come the pathogen and repair the damage. The second point is that the classification is really rather simple and obvious.
Now for the third point: When and by whom do you think the ideas in this chapter were first proposed? Was it by some nineteenth- century medical researcher building on the ideas of Pasteur and Dar- win as well as the rapidly expanding body of knowledge of parasite life histories? No.
