## **Core Concept**
The question assesses knowledge of infectious diseases and the concept of healthy carriers, who are individuals that harbor a pathogen but do not exhibit symptoms and can transmit the disease to others. This concept is crucial in epidemiology and public health.

## **Why the Correct Answer is Right**
Typhoid fever, caused by *Salmonella Typhi*, is well-known for having healthy carriers. A famous example is "Typhoid Mary," who was a healthy carrier of *Salmonella Typhi*. Hepatitis B and C are also known to have healthy carriers who can transmit the virus to others. However, rabies is primarily transmitted through the saliva of infected animals, usually through a bite. Healthy carriers of rabies are not typically identified or documented because the disease is almost invariably fatal once symptoms appear, and the infectious period is usually associated with the onset of symptoms.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Typhoid carriers can indeed be healthy. *Salmonella Typhi* can colonize the gallbladder of asymptomatic individuals, who then serve as reservoirs for infection.
- **Option B:** Hepatitis B has a significant number of healthy carriers worldwide. These carriers can transmit the virus to others through bodily fluids.
- **Option C:** Hepatitis C also has healthy carriers, although the term "carrier" is less commonly used; instead, the focus is on chronic infection. Individuals with chronic hepatitis C can transmit the virus.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that while healthy carriers are a significant public health concern for diseases like typhoid and hepatitis B and C, diseases like rabies do not have a carrier state in the traditional sense. Rabies transmission is almost exclusively through direct contact with infected saliva.

## **Correct Answer:** D. Rabies.