Chapter 1

Introduction. The basics: infections, transmission and models

This chapter, written by Paul EM Fine (Professor of Infectious Disease Epidemiology at the London School of Hygiene & Tropical Medicine) provides an introduction to the epidemiology of infections and models. It covers the key features of infections and the reasons for the occurrence of epidemics. In addition, it discusses the key concepts in infectious disease epidemiology and factors influencing control, namely the basic and net reproduction numbers and the herd immunity threshold. This is followed by a discussion of what we mean by a mathematical model.


Data on the numbers of cases of influenza-like-illness reported during the 1957 (Asian) influenza epidemic to a general practitioners’ practice in Wales (Ministry of Health, 1960).

Data such as these are frequently used by infectious disease modellers.

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