Field epidemiology and outbreak investigation

This chapter introduces the principles and practice of epidemiology for disease control as applied to outbreak response through the lens of “field epidemiology”. Applied or “field” epidemiology is primarily concerned with producing timely contextual information to intervene when public health problems arise, often using messy primary data. To advance beyond the military and colonial legacies of the discipline, the term “field epidemiology” will likely, and should, be phased out in favour of terms such as “applied” or “intervention” epidemiology. We will nevertheless, for the purpose of this chapter, use the term “field epidemiology”.The role of a field epidemiologist in investigating and responding to outbreaks of any aetiology can be summarised in ten common steps: preparing for field work, confirming the diagnosis, determining the existence of an outbreak, identifying and registering cases, descriptive analysis, statistical analysis, drawing conclusions, communicating findings, implementing interventions, and evaluating the response as well as continued surveillance. We demonstrate these steps using a hypothetical outbreak scenario, with questions for the reader, and highlight that in practice, these steps do not necessarily happen in succession, multiple steps can happen simultaneously or not at all, and outbreak response is an iterative process.