Epidemiology Fundamentals

Outbreak Investigation

• Definition: A systematic and structured process to identify and control the source of an outbreak
• Steps:
  1. Verification: Confirm the existence of an outbreak
  2. Initial case finding: Identify and collect data on initial cases
  3. Case definition: Develop a clear definition of a case to identify additional cases
  4. Case finding: Identify and collect data on all cases
  5. Descriptive epidemiology: Describe the outbreak in terms of person, place, and time
  6. Hypothesis generation: Develop hypotheses about the source of the outbreak
  7. Analytic epidemiology: Test hypotheses through data analysis
  8. Intervention and control: Implement control measures to stop the outbreak
  9. Evaluation: Assess the effectiveness of control measures

Infectious Diseases

• Definition: Diseases caused by the presence of pathogens (bacteria, viruses, fungi, parasites)
• Types:
  • Bacterial: e.g., tuberculosis, pneumonia
  • Viral: e.g., influenza, HIV
  • Fungal: e.g., candidiasis
  • Parasitic: e.g., malaria, hookworm
• Modes of transmission:
  • Direct contact: Skin-to-skin contact
  • Indirect contact: Contaminated surfaces, fomites
  • Airborne transmission: Respiratory droplets
  • Vector-borne transmission: Insect vectors (e.g., mosquitoes)
  • Food and water transmission: Contaminated food and water

Disease Surveillance

• Definition: Ongoing, systematic collection and analysis of data on diseases and health-related events
• Purposes:
  • Early detection of outbreaks
  • Monitoring disease trends and patterns
  • Evaluating the effectiveness of interventions
• Types:
  • Passive surveillance: Relying on reports from healthcare providers
  • Active surveillance: Proactive case finding and data collection
  • Sentinel surveillance: Focused surveillance on specific populations or diseases

Epidemiological Study Designs

• Observational studies:
  • Cohort studies: Follow a group of people over time to observe outcomes
  • Case-control studies: Compare cases with controls to identify risk factors
  • Cross-sectional studies: Examine a population at a single point in time
• Experimental studies:
  • Randomized controlled trials (RCTs): Intervene and measure the effect
  • Field trials: Test interventions in real-world settings

Risk Factor Analysis

• Definition: Identifying and quantifying factors that increase the likelihood of developing a disease
• Types of risk factors:
  • Demographic factors: Age, sex, ethnicity
  • Behavioral factors: Smoking, physical activity, diet
  • Environmental factors: Exposure to toxins, radiation
• Measures of association:
  • Odds ratio (OR): Ratio of odds of disease in exposed vs. unexposed groups
  • Relative risk (RR): Ratio of incidence rates in exposed vs. unexposed groups
  • Attributable risk: Proportion of cases attributed to a risk factor