M.D. We often think of infection as something that befalls us as a consequence of forces beyond our control.
Epidemics seem to have a mysterious dynamic, arising unexpectedly and subsiding inexplicably.
But science shows that this impression is inaccurate. While the determinants of epidemics are undoubtedly complex, they are understandable. In this lecture on interactions between viral pathogens and their hosts, Dr. Ganem will consider some of the forces that create and shape epidemic infection. New infectious diseases usually result from an upset in a previously established balance between the virus and its natural host. Mutations or other genetic changes in the virus, for example, may confer upon it new properties, such as the ability to grow more efficiently in its natural host or to spread to a species that is not ordinarily susceptible.