Medical researchers are not the only ones who deal with conflicts between organisms. Ecologists and animal- behavior specialists routinely deal with predator- prey relationships, struggles between males for mating
opportunities, and many other sorts of conflict. They recognize the evolutionary significance of the phenomena they observe and use such terms as strategy and tactic, winner and loser, and other indications of commitment to the adaptationist program. This approach has been richly rewarding for ecologists and others who are steeped in Darwin- ism. A similar approach to phenomena such as fever ought to be sim- ilarly rewarding in a field of such vital interest to all of us.
The contest between parasites and their hosts is a war, and every sign and symptom of infection can be understood in relation to the underlying strategies of one or the other belligerent. Some, like fever and iron withholding, benefit the host (defenses); others ben- efit the pathogen; and a few are incidental effects of the war between them. The strategies are not, of course, products of conscious thought, but they are strategies nonetheless. Bacteria that sneak into the body by pretending to be harmless are rather like Greek soldiers hiding in a wooden horse. When the manifestations of infection are related to conflicting interests, they fit neatly into cat- egories based on their functional importance.