Epidemic theory - what is it?

Using diagrams, Dr. Lowell J. Reed first describes the history of epidemics, the origins of disease, using measles and small pox as examples, and means of transmission. He then demonstrates the epidemic theory where St is the number of people susceptible to the disease over time multiplied by 1 minus qct (the probability of a person with the disease meeting a susceptible person) equals C t+1(cases over time). Also factored into this equation is the number of people who develop an immunity to the disease after recovering from it. The theory is then tested against experience. Dr. Reed sets up an experiment demonstrating the practical application of the theory using a model. He then discusses epidemic control focusing on isolation of people who already have the disease, and immunization of people who are susceptible to the disease.