Principles of outbreak investigation

Outbreak investigation is an essential function of public health professionals. It is an opportunity to gain new knowledge of diseases and to discover the weaknesses of current public health practices and systems. Unfortunately, most outbreaks are not investigated. This chapter will present the principles and important points about outbreak investigation. The reader will learn about how to detect outbreaks from routine official surveillance and unofficial sources. The reader can assume oneself as an investigator who has to organize the team, review previous knowledge, and prepare the technical and management aspects, before starting the investigation. The reader will learn about the major ten steps in the investigation, with examples, which starts by confirming the existence of the outbreak, verifying the diagnosis, gathering case information, descriptive epidemiology, formulating and testing the hypothesis when necessary, conducting environmental surveys to supplement epidemiological evidence, providing timely on-site reporting of the findings, with practical recommendations to local and national responsible authorities, and communicating risk to health professional community and public. The reader is reminded about the need to follow-up on the recommendations and continue vigorous surveillance of the health problem. The chapter ends by forecasting more joint international investigations to control emerging diseases and new problems. After reading this chapter, the reader should be clear that outbreak investigation is an interesting, challenging, and important task requiring a competent investigator who combines sound scientific knowledge and good management.