Experimental Analysis of Genetic Determinants in Resistance to Infectious Disease*

Problems of infectious disease susceptibility and resistance have been extensively studied by the epidemiologist, the bacteriologist, and the geneticist. The objectives of these scientists, although expressed differently, have much in common. The epidemiologist, chiefly through the study of spontaneous epidemics, seeks to specify the factors that affect the initiation, the spread, and the regression of the disease. The bacteriologist's considerations are (1) to assign a pathogen as the specific causative agent for the disease and (2) through treatments of this agent to generate means of controlling the disease. The geneticist utilizes both of these approaches as fundamental to his problem but, in addition, directs his attention to the questions of why there should be variations in survival of the hosts that may be exposed to the disease and why comparable variations are observed in pathogen virulence.