Chapter 1 Introduction

There is no single education and training activity that prepares public health trainees and graduate students for the rigors, depth, breadth, and diversity of public health science and practice than conducting outbreak investigations. The science and art of conducting outbreak investigations provides learning opportunities. Outbreak investigations are complex, fast-paced, and conducted by a multidisciplinary team operating in a high-pressure, rapidly changing, and uncertain environment. Investigators must be agile, open-minded, and flexible, yet tenacious and methodologically rigorous in pursuing evasive causal explanations in order to intervene and protect the public.

Conducting an outbreak investigation is commonly summarized in ten steps (Gregg 2008): (1) Determine the existence of the epidemic; (2) Confirm the diagnosis; (3) Define a case and count cases; (4) Orient the data interms of time, place, and person; (5) Determine who is at risk of becoming ill; (6) Develop a hypothesis that explains the specific exposure that caused disease and test this hypothesis by appropriate statistical methods; (7) Compare the hypothesis with the established facts; (8) Plan a more systematic study; (9) Prepare a written report; and (10) Execute control and prevention measures.

Alternatively, one can use an eight step approach (MacDonald 2011): (1) Verify the diagnosis and confirm the outbreak; (2) Define a case and conduct case finding; (3) Tabulate and orient data: time, place, and person; (4) Take immediate control measures; (5) Formulate and test hypothesis; (6) Plan and execute additional studies; (7) Implement and evaluate control measures; and (8) Communicate findings.

The Centers for Disease Control and Prevention uses 13 steps (???).2 In this book, we cover the same material but organized under seven conceptual steps based on how disease intervention specialists (DISs) work at local health departments. On a daily basis, DISs investigate and manage individual “cases.” Now, in an outbreak investigation, they investigate a group of cases (case investiation) with the purpose of drawing conclusions about what is causing this outbreak in order to control it. Here are the seven conceptual steps:

Table: Conducting an outbreak investigation in 7 steps (or less)

1. Case investigations | 2. Continue (or start) surveillance | 3. Cause investigations | 4. Control and prevention measures (do early) | 5. Conduct analytic study (if necessary) | 6. Conclusions (enhancing valid inferences) | 7. Communicate findings |


Gregg, Michael. 2008. Field Epidemiology. Oxford University Press.

MacDonald, Pia D.M. 2011. Methods in Field Epidemiology. Jones & Bartlett Learning.