Identification of cholera by Snow is an example of?
**Core Concept**
The question is testing the concept of epidemiological investigation techniques, specifically the identification of cholera by John Snow in 1854. This event marked a significant milestone in the history of epidemiology, demonstrating the importance of observation, mapping, and intervention in controlling outbreaks.
**Why the Correct Answer is Right**
The correct answer is related to the epidemiological investigation technique used by John Snow, which involved mapping the cases of cholera in London and identifying the source of the outbreak. Snow's investigation led him to conclude that the outbreak was caused by a contaminated water pump on Broad Street (now Broadwick Street). He successfully advocated for the removal of the pump handle, which stopped the spread of the disease. Snow's work exemplified the use of spatial analysis and intervention to control an outbreak, illustrating the concept of **Epidemiological Mapping**.
**Why Each Wrong Option is Incorrect**
* **Option A:** Although Snow's work involved observation and mapping, it is not an example of **Case-control study**, which is a research design used to compare individuals with a specific outcome (cases) to those without the outcome (controls).
* **Option B:** **Randomized Controlled Trial (RCT)** is a type of clinical trial that involves random assignment of participants to different groups, which is not relevant to Snow's investigation of cholera.
* **Option C:** **Cohort Study** is a type of longitudinal study that involves following a group of individuals over time, which is not the primary method used by Snow in identifying the cholera outbreak.
**Clinical Pearl / High-Yield Fact**
John Snow's work on the cholera outbreak in London is often considered the first major study in the field of epidemiology, demonstrating the importance of observation, mapping, and intervention in controlling outbreaks.
**Correct Answer:** D.