The study of infectious disease and immunity focuses on those interactions between infectious agents, their human and other hosts, and their relationship to the environment that may lead to disease in humans. Infectious disease agents include primarily pathogenic bacteria, fungi, helminths, protozoa and viruses that continue to be leading causes of morbidity and mortality in human populations throughout the world. The treatment, control and prevention of infectious diseases depend upon an in depth knowledge of the biology and genetics of the pathogen; the factors that allow pathogens to infect, persist in the host and produce disease; and the host's defense mechanisms that bring about recovery. This requires an integration of the disciplines of molecular and cellular biology, genetics, immunology, microbiology (which includes virology, bacteriology, mycology and parasitology) and epidemiology.
