The exercises (6.1 to 6.9) address the core principles of investigating an outbreak using epidemiological methods including statistical analysis. Outbreaks are defined as “unexpected events,” which often receive sufficient media attention to warrant rapid public relations or action responses (Lesson 6: Investigating an Outbreak). Therefore, it is important to understand the principles of epidemiological methods like those offered in the exercises. In addition to the exercises (6.1 to 6.9) the CDC also offers the self-assessment quiz. The exercises and the quiz collectively summarize the main issues related to outbreaks and how an epidemiologist would address different types of outbreaks in different scenarios. 6.1. This exercise addresses the concept of clustering, in which a relatively small group of cases seems confined to a specific geographical area. For example, there may be reports of a certain type of cancer in an area where the drinking water is contaminated. Further investigation is warranted even if the cases will later be determined to be unrelated. The epidemiologist will first look at prevalence rates in other communities and compare with the target population. If anomalies are detected, the epidemiologist would develop hypotheses such as whether the target community shared a common genetic pool or whether there were...

Environmental causes could be related to weaknesses in the healthcare services industry as well as to factors like pollution.
6.2. This exercise pertains to infectious disease. Some infectious diseases have incubation periods, making the development of accurate data difficult. Moreover, some infectious diseases like West Nile virus are seasonal, requiring the epidemiologist to track the data over time within the same community. The term “outbreak” can be used to describe population anomalies, a number of cases that significantly exceeds the norm for that same period of time in that same geographic area.

6.3. What constitutes an official “case” is one of the central questions in epidemiology, and the answer will vary depending on the disease. Operationalized definitions of the disease are critical for accurate data, and evidence-based responses to outbreaks. Case definitions are offered for eosinophilia, with the results of this data showing that Patient 4 and Patient 7 cannot be classified as “cases,” but the others can, according to the definitions of eosinophilia given.

6.4. This exercise is about an outbreak of gastroenteritis with a table referring to purported cases. The key here is to look for degree of certainty, taking into account the different…