**Core Concept**
Negri bodies are characteristic intracytoplasmic inclusions found in the neurons of individuals infected with rabies virus. They are a key diagnostic feature of the disease, which is caused by the rabies virus, a lyssavirus.

**Why the Correct Answer is Right**
Negri bodies are formed as a result of the replication of the rabies virus within the neurons. The virus causes the host cell's cytoplasm to become filled with viral nucleocapsids, which are then surrounded by a membrane, forming the characteristic inclusions. The presence of Negri bodies in the brain tissue is a crucial finding for the diagnosis of rabies, and they are typically found in the hippocampus, cerebellum, and other areas of the brain.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Negri bodies are not associated with the infection caused by the Nipah virus, which also affects the brain but does not produce these characteristic inclusions.
**Option B:** This option is incorrect because the presence of Negri bodies is not a feature of Alzheimer's disease, which is a neurodegenerative disorder caused by the accumulation of amyloid plaques and tau protein in the brain.
**Option C:** This option is incorrect because the infection caused by the Japanese encephalitis virus does not produce Negri bodies, and the two diseases have distinct pathologies.

**Clinical Pearl / High-Yield Fact**
Rabies is a fatal disease if left untreated, and prompt post-exposure prophylaxis (PEP) is essential for preventing the development of the disease. The presence of Negri bodies in the brain tissue is a definitive diagnostic feature of rabies, and their identification is critical for confirming the diagnosis in suspected cases.

**Correct Answer: D.**