EIS Case Studies

Epidemic Intelligence Service (EIS) Officers in classroom.
Epidemic Intelligence Service (EIS) Officers learn applied epidemiology through a CDC case study.

Case Studies in Applied Epidemiology

CDC developed case studies in applied epidemiology based on real-life epidemiologic investigations and used them for training new Epidemic Intelligence Service (EIS) officers — CDC’s “disease detectives.” EIS offers these carefully crafted epidemiology case studies for schools of medicine, nursing, and public health to use as a component of an applied epidemiology curriculum.

The following case studies use specific examples to teach epidemiology concepts, require active participation, and help strengthen problem-solving skills. These case studies in applied epidemiology:

Cover epidemiologic basics, including:

  • Outbreak investigation
  • Surveillance
  • Study design
  • Data interpretation
  • Descriptive and analytic methods

Are based on public health investigations of:

  • Infectious diseases
  • Chronic illnesses
  • Environmental health

Instructor and Student Guides

Each EIS Case Study consists of an instructor guide or a student guide.

  • Instructors or trainers (not students): obtain Applied Epidemiology Case Studies instructors’ guides. Send an e-mail to: eis@cdc.gov and label subject line: “Case Study Instructor Guide Request”.
  • Students: Use Adobe Acrobat reader, to view or print the student guides.

How to Use the EIS Case Studies

Students may practice their epidemiologic skills by using these exercises in classroom activities or as homework assignments to reinforce principles and skills previously covered in lectures and reading assignments.

  • In-Class Activity
    Students, read the case study up to the first question and then perform calculations, construct graphs, or discuss the answer. Students may be asked to play different roles in answering the question. After discussing the first answer satisfactorily, read on to the next question and continue with the exercise.
  • Individual Activity
    Students, for a homework assignment, read the case study and answer the questions, then discuss the findings in class.

An Epidemic of Thyrotoxicosis

Student Guide #873-703 Cdc-pdf[PDF – 16 pages]. Case study based on a 1985 outbreak with unknown etiology and mode of transmission in multiple states. Updated in 2003.

Learning Objectives

After completing this case study, students should be able to

  • List the key tasks involved in investigating epidemics of unknown cause
  • Describe the roles, responsibilities, and relationships of federal versus state public health agencies in a field investigation
  • Assign appropriate priority to key tasks during an investigation
  • Describe jurisdictions of health agencies at various levels of government
Cigarette Smoking and Lung Cancer

Student Guide #731-703 Cdc-pdf[PDF – 12 pages]. Case study based on the classic studies of Doll and Hill in the 1950s. Addresses study design, interpretation of measures of association, and impact of association. Updated in 2003.

Learning Objectives

After completing this case study, students should be able to

  • Discuss the elements of study design, and the advantages and disadvantages of case-control versus prospective cohort studies
  • Discuss some of the biases which might have affected these studies
  • Calculate a rate ratio, rate difference, odds ratio, and attributable risk percent
  • Interpret each measure and describe each measure’s use
  • Review the criteria for causation
Oral Contraceptive Use and Ovarian Cancer

Student Guide #811-705 Cdc-pdf[PDF – 15 pages]. Case study based on a 1980–1982 multicenter case-control study. Addresses bias and analysis of case-control studies. Updated in 2005.

Learning Objectives

After completing this case study, students should be able to

  • Outline the sequence of an epidemiologic analysis
  • Discuss the biases of particular concern in case-control studies and ways to minimize their influence
  • Describe why and when to use crude and adjusted odds ratios and 95% confidence intervals, and how to interpret them
  • Define and recognize effect modification and confounding
Oswego: An Outbreak of Gastrointestinal Illness Following a Church Supper

Student Guide #401-303 Cdc-pdf[PDF – 12 pages]. Case study of a classic, straightforward outbreak investigation in a defined population. Based on a 1940 outbreak of Staphylococcus aureus among church picnic attendees. Additional material: Compendium of Acute Foodborne and Waterborne Diseases Cdc-pdf[PDF – 7 pages]. Updated in 2003.

Learning Objectives

After completing this case study, students should be able to

  • Define the terms cluster, outbreak and epidemic
  • List the steps in the investigation of an outbreak
  • Draw, interpret and describe the value of the epidemic curve
  • Calculate and compare food-specific attack rates to identify possible vehicles
  • List reasons for investigating an outbreak that has apparently ended
Paralytic Illness in Ababo

Student Guide #891-903Cdc-pdf[PDF – 11 pages]. Case study of a surveillance system. Updated in 2003.

Learning Objectives

After completing this case study, students should be able to

  • Define incidence, prevalence, and case-fatality rate
  • Define surveillance and identify the key features of a surveillance system
  • List the types of information that should be collected on a surveillance case report form
  • List the factors that can account for a change in the reported incidence of a disease
  • Define sensitivity of a surveillance system, and the effect of different case definitions on sensitivity
Screening for Antibody to the Human Immunodeficiency Virus

Student Guide #731-705 Cdc-pdf[PDF – 12 pages]. Case study of a hypothetical health department anticipating the release of the first HIV antibody test in 1985. Focus is on screening. Updated in 2003.

Learning Objectives

After completing this case study, students should be able to

  • Define and perform calculations of sensitivity, specificity, predictive-value positive and predictive-value negative
  • Describe the relationship between prevalence and predictive value
  • Discuss the trade-offs between sensitivity and specificity
  • List the principles of a good screening program
Suspected Legionnaires’ Disease in Bogalusa

Student Guide #912-303 Cdc-pdf[PDF – 16 pages]. Case study based on a community outbreak of Legionnaires’ disease in Bogalusa, Louisiana in 1989. Addresses the steps of a field investigation and a case-control study.. Updated in 2003.

Learning Objectives

After completing this case study, students should be able to

  • Discuss the relationship between and roles of state-based and Atlanta-based EIS officers in a field investigation
  • Develop an epidemiologic case definition
  • Calculate power for a case-control study
  • Describe different sources of controls for a community-based outbreak
Surveillance for E. coli 0157:H7—Information for Action

Student Guide #941-903 Cdc-pdf[PDF – 19 pages]. Case study based on surveillance and investigation activities of the Oregon Health Division between 1986 and 1995. Updated in 2003.

Learning Objectives

After completing this case study, students should be able to

  • List the process and criteria for placing a disease or condition on a state or national notifiable disease list
  • List the categories of information that should be included in a surveillance instrument
  • Summarize and interpret surveillance data
  • Recognize difficulties in balancing public health concerns with consumer and industry considerations in emerging issues
Texarkana — Epidemic Measles in a Divided City

Student Guide #711-903 Cdc-pdf[PDF – 12 pages]. Case study based on an infectious disease outbreak investigation in Texas.

Learning Objectives

After completing this case study, students should be able to

  • Discuss the advantages and disadvantages of using a sensitive and/or specific case definition in an epidemic investigation
  • Calculate vaccine efficacy and discuss its interpretation
  • Discuss the advantages and limitations of selecting a specific age as the recommended target date for administering vaccinations