Parasitology is the study of parasites, their hosts, and the relationship between them. Every free-living species has its own unique species of parasite - humans included - such that the number of parasitic species greatly exceeds the number of free-living species. Parasites in humans result in millions of deaths each year throughout the world, but particularly in the developing world. Researchers in the Department are interested in studying the effects of parasites upon the human population, looking at the epidemiology of parasitic diseases such as malaria and sleeping sickness, the cellular mechanisms by which the parasite infects the host and causes disease, and the reaction of the immune system to the parasite.