**Core Concept**
Typhoid fever is a systemic infection caused by Salmonella Typhi, characterized by fever, headache, and abdominal pain. The pathogenesis of typhoid involves the invasion of the bacteria into the intestinal mucosa and subsequent spread to the bloodstream, lymphoid tissues, and other organs.

**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of typhoid fever. The bacteria invade the intestinal mucosa, causing damage to the epithelial cells and leading to the production of inflammatory cytokines. This results in the characteristic symptoms of typhoid, including fever, headache, and abdominal pain. The bacteria also invade the lymphoid tissues, such as the Peyer's patches, which can lead to the development of typhoid ulcers.

**Option A:** Typhoid fever is caused by Salmonella Paratyphi.
* Incorrect because while Salmonella Paratyphi can cause enteric fever, it is a different species from Salmonella Typhi and is more commonly associated with paratyphoid fever.

**Option B:** Typhoid fever is characterized by the presence of rose spots.
* Incorrect because while rose spots can be a feature of typhoid fever, they are not a universal finding and are more commonly associated with typhoid in children.

**Option C:** Typhoid fever is typically self-limiting.
* Incorrect because while some cases of typhoid fever may be self-limiting, many cases require antibiotic treatment to prevent complications and reduce the risk of transmission.

**Option D:** Typhoid fever is transmitted through the fecal-oral route.
* Incorrect because while the fecal-oral route is a common mode of transmission for typhoid fever, it is not the only route and other modes of transmission, such as contaminated food and water, are also possible.

**Clinical Pearl / High-Yield Fact**
The Widal test, which measures the level of antibodies against Salmonella Typhi in the blood, is often used to diagnose typhoid fever. However, this test is not always reliable and can produce false-negative results, especially in the early stages of the disease.

**Correct Answer:** D. Typhoid fever is transmitted through the fecal-oral route.