Patterns of Disease & Control Measures
Once an outbreak is confirmed, the next goal is to identify patterns (person, place, time) and implement control measures at the appropriate level of the natural history of disease. Understanding epi curves and transmission chains is critical for high-level scoring.
Key Points
- Common source → sharp peak, then rapid decline
- Point source → all exposed at once (e.g. wedding salad)
- Propagated → multiple waves (person-to-person)
- Mixed → common + propagated
- Control at source: remove contaminated food, treat cases
- Control at transmission: hand hygiene, masks, quarantine
- Control at host: vaccination, chemoprophylaxis
Formulas & Concepts
Secondary Attack Rate:SAR = (New cases in contacts ÷ Total susceptible contacts) × 100
Reproduction Number (R):R₀ = average number infected by one case in susceptible population