ABSTRACT
Our emphasis in this text is, of course, microorganisms-living things ordinarily too small to see with the unaided eye. In addition to prokaryotes, viruses, fungi, and protozoa, humans are susceptible to infection with a variety of much larger worms, known as helminths. Helminths represent an important category of nonmicroscopic parasites. A parasite is any organism, microscopic or not, that lives in or on another organism, from which it obtains a place to live and reproduce and a source of nutrients. Our fi nal example of how history can be shaped by disease involves such a helminth parasite. Specifi cally we will discuss how an outbreak of schistosomiasis may have infl uenced the geopolitical landscape in the early days of the Cold War.
