Epidemiology can be considered, quite simply, the study of epidemics. There are several possible definitions of an epidemic, and the one we prefer is EPIDEMIC: Change in disease intensity in a host population over time and space. We generally do not overly emphasize the nuances of definitions in this book, but it is helpful here for instructional purposes to consider the components of this definition of an epidemic. First of all, the use of “change” emphasizes that epidemics are dynamic processes, and many aspects of their study involve characterizing rates of change. The use of “disease” emphasizes that epidemics specifically involve diseases, and not just pathogens or hosts. “Intensity” is a general term that characterizes the magnitude of disease or the infection. The use of “host population” emphasizes that an epidemic is primarily a population phenomenon, involving in this case, a population of plants susceptible to one or more species of pathogen. Finally, “time” and “space” are indications of the two physical dimensions over which the dynamic process of an epidemic occurs. Specifically, disease intensity varies from time to time and from location to location during epidemics.

Chapter topics include:

  • Plant Disease Epidemics

  • Concepts: Epidemics, Epidemiology, and Epidemic versus epiphytotic

  • Historical Developments

  • Prelude to the Rest of the Book

  • Possible Course Outlines

  • Suggested Readings