## **Core Concept**
The World Health Organization (WHO) has specific criteria to classify leprosy as a public health problem based on its prevalence. Leprosy, also known as Hansen's disease, is a chronic infection caused by *Mycobacterium leprae*. The prevalence is typically measured as the number of cases per population.

## **Why the Correct Answer is Right**
The WHO has set a goal to eliminate leprosy as a public health problem, which is defined as a prevalence of less than 1 case per 10,000 population. This criterion helps in assessing the burden of the disease and the effectiveness of control measures. Therefore, if the prevalence is 1 or more cases per 10,000 population, leprosy is considered a public health problem.

## **Why Each Wrong Option is Incorrect**
* **Option A:** This option suggests a higher threshold than the correct one, which does not align with the WHO's definition for public health concern.
* **Option B:** This option suggests a much higher threshold, which is not relevant to the current public health criteria for leprosy.
* **Option D:** This option suggests a lower threshold than the correct one, which, although seemingly more stringent, does not match the WHO's specified criterion.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the WHO's definition of elimination of leprosy as a public health problem is a prevalence of less than 1 case per 10,000 population. This is crucial for public health policy and for monitoring the success of leprosy control programs.

## **Correct Answer:** C. 1 case per 10,000 population.