Epidemiology and Disease Surveillance

Problem-based learning tasks on outbreak investigation, vaccine surveillance, integrated health systems, and occupational epidemiology.
Epidemiology
Surveillance
Public Health
Assignment
Author

Kostadin Kostadinov

Published

March 1, 2026

Practical Class Instructions:

This document contains a series of interactive scenarios designed for group work in social medicine and public health workshops. Each group will work through a specific case study to design surveillance systems, calculate key epidemiological indicators, and debate the best course of action during public health crises.

Reference Material

This assignment is based on the reading material: Risk Factors, Causality, and Morbidity Measurement. All methodological justifications and critiques must reference concepts from this text.

General Instructions for Students

Each group will independently solve a distinct epidemiological problem. Your task is to:

  1. Organize the Epi System: Propose a surveillance framework (active vs. passive, syndromic, or integrated) and justify your choices based on the scenario’s constraints.
  2. Perform the Calculations: Solve the requested indicators (Attack Rate, Relative Risk, Vaccine Effectiveness, etc.) using the provided data. Show all working.
  3. The Battle (Debate): Prepare to defend your suggested control measures and debate the trade-offs in different surveillance strategies.

Case 1: “The Festival Fever”

Outbreak Surveillance and Response

Scenario: A major three-day music festival attracts 50,000 attendees to a rural county. By the second evening, the local emergency department reports a sudden influx of 45 patients with severe vomiting and abdominal pain. You are the lead epidemiological team tasked with investigating this potential outbreak.

Organize the Epi System:

You must implement a “drop-in” syndromic surveillance system. Decide which data sources to use (e.g., first-aid station logs, local pharmacies, or hospital “chief complaint” records). Define a preliminary case definition to identify symptomatic individuals without waiting for lab confirmation.

Calculate the Indicators:

  1. Attack Rate: Based on a sample of 500 attendees from one specific campsite where 60 are ill, calculate the attack rate for that group.
  2. Relative Risk (RR): If 45 ill people ate at “Vendor A” (total 200 eaters) and 15 ill people did not (total 300 non-eaters), calculate the RR for Vendor A.
  3. Odds Ratio (OR): Use a 2x2 table to calculate the OR for specific food items if a full cohort cannot be identified.

Work Together & Discuss:

  • Suggestion: Propose immediate control measures (e.g., “callback” of products or closing specific vendors) before lab results arrive.
  • Battle Point: One group argues for active case finding (visiting tents) while another advocates for passive surveillance (waiting for clinic reports). Debate the trade-offs in timeliness vs. resources.

Case 2: “The Silver Shield Program”

Vaccine Surveillance

Scenario: The Ministry of Health is rolling out a new influenza vaccine for citizens over 65. Within two weeks, rumors circulate on social media that the vaccine is causing neurological tremors. Public confidence is dropping.

Organize the Epi System:

Design a Phase IV post-marketing surveillance system. You must choose between a passive reporting system (doctors send in reports) or an active sentinel network of 50 designated geriatric clinics.

Calculate the Indicators:

  1. Vaccine Coverage: If 150,000 doses were distributed to a target population of 500,000 elderly citizens, calculate the coverage.
  2. Vaccine Effectiveness (VE): Using the screening method, if the proportion of cases vaccinated (PCV) is 20% and the population coverage (PPV) is 60%, estimate the VE.
  3. Standardized Morbidity Ratio (SMR): Compare the observed tremors in the vaccinated group against the “expected” tremors based on historical rates in the general elderly population.

Work Together & Discuss:

  • Suggestion: How should the “risk communication” be handled to address social media rumors without causing more panic?
  • Battle Point: Discuss the “Healthy Vaccinee Effect”—are the people getting the vaccine inherently healthier, and does this bias your effectiveness indicators?

Case 3: “District Health Reform”

Integrated Information Systems

Scenario: You are consultants for a developing region (“Region X”) that suffers from fragmented health data. HIV, Tuberculosis (TB), and Maternal Health data are all kept in separate, non-linkable paper logs. This “over-surveillance” is exhausting local nurses.

Organize the Epi System:

Implement the “Golden Rule” of health information systems: design one single register per population unit. Propose an Integrated Disease Surveillance and Response (IDSR) framework that uses a single weekly reporting form for multiple conditions.

Calculate the Indicators:

  1. Point Prevalence: Calculate the TB prevalence in a village of 2,000 people on Jan 1st where 40 cases are currently on the register.
  2. Period Prevalence: If 10 new cases are diagnosed during the year, calculate the Period Prevalence for that calendar year.
  3. Incidence Density: Calculate the TB incidence rate using person-time at risk for 100 people followed over 6 months who generated 5 new cases.
  4. Infant Mortality Rate (IMR): In a year with 1,200 live births and 60 deaths of children under age 1, calculate the IMR.

Work Together & Discuss:

  • Suggestion: Propose using “verbal autopsies” to identify causes of death in areas where physicians are rare.
  • Battle Point: Use the “Iceberg Metaphor” to discuss why your indicators might be significantly under-reported. How do you estimate the “underwater” portion of the disease burden?

Case 4: “The Industrial Lung Study”

Occupational Surveillance

Scenario: A large mining corporation is being sued by former employees who claim that silica dust exposure caused a cluster of lung diseases. The company claims the rates are no higher than the general population.

Organize the Epi System:

Organize a non-concurrent (historical) cohort study. You must perform record linkage between the company’s payroll/union lists (to define exposure) and national death certificates or cancer registries (to define outcomes).

Calculate the Indicators:

  1. Cumulative Incidence (10-year Risk): If 50 lung disease cases were diagnosed among 500 miners followed for 10 years, calculate the CI.
  2. Attributable Risk among the Exposed (ARE): If the risk of disease in exposed miners is 0.15 and in unexposed office staff is 0.03, calculate the fraction of disease actually attributable to the mine.
  3. Population Attributable Risk (PAR): If 30% of the town works in the mine, calculate how much the town’s total lung disease would drop if the mine exposure were eliminated.

Work Together & Discuss:

  • Suggestion: Propose Standard Operating Procedures (SOPs) for future dust-level measurements to ensure high-quality data for the next 10 years.
  • Battle Point: Discuss confounding by smoking behavior. Since the historical records don’t list who smoked, how does this “unfocused datascope” affect your ability to blame the mining dust?

Evaluation Criteria:

  • Epidemiological Logic (40%): Correct application of surveillance principles and study design concepts.
  • Mathematical Accuracy (30%): Correct calculation of indicators and selection of denominators.
  • Synthesis & Defense (20%): Ability to justify control measures and navigate ethical/resource trade-offs.
  • Professional Communication (10%): Clarity and precision of group presentation.