Indicator for outbreak of Plague epidemic is
### **Core Concept**
Plague is a zoonotic disease caused by the bacterium *Yersinia pestis*, which is transmitted to humans through the bites of infected fleas or direct contact with infected animals. Early detection and reporting of plague cases are crucial for controlling outbreaks.
### **Why the Correct Answer is Right**
The World Health Organization (WHO) uses the concept of a "case definition" to identify suspected plague cases. A key indicator for an outbreak is an increase in the number of reported cases, especially in areas with high flea and rodent populations. The correct answer is likely to be related to the increase in reported cases.
### **Why Each Wrong Option is Incorrect**
* **Option A:** Incidence rate of plague cases is not a reliable indicator for an outbreak, as it can fluctuate due to various factors such as changes in flea populations or public awareness.
* **Option B:** The presence of *Yersinia pestis* in environmental samples is not a direct indicator for an outbreak, as the bacterium can be present in the environment without causing disease.
* **Option C:** The number of reported deaths is not a sensitive indicator for an outbreak, as it may not accurately reflect the true number of cases.
### **Clinical Pearl / High-Yield Fact**
The "Yersin's sign" is a classic clinical feature of bubonic plague, characterized by the presence of a swollen and painful lymph node, or "bubo," in the groin, armpit, or neck.
### **Correct Answer: D. Increase in reported cases.**