## Core Concept
Japanese encephalitis (JE) is a mosquito-borne flavivirus infection that primarily affects the central nervous system (CNS). It is prevalent in Asia, including India, and is a significant cause of acute encephalitis in these regions. The virus is mainly transmitted by the *Culex* mosquito.

## Why the Correct Answer is Right
The correct statement regarding Japanese encephalitis needs to be identified by evaluating each option. However, since the specific details of the options A, B, C, and D are not provided, we will proceed with a general understanding of JE. Typically, JE virus infection can lead to severe neurological symptoms, and it's known for its high mortality rate and long-term neurological sequelae.

## Why Each Wrong Option is Incorrect
Without specific details on the options, let's consider general misconceptions about JE:
- **Option A:** If a statement claims JE is primarily spread through direct human-to-human contact, it would be incorrect because JE is mainly transmitted through mosquito vectors.
- **Option B:** If a statement suggests JE is caused by a bacterium, it would be incorrect because JE is caused by a virus, specifically a flavivirus.
- **Option C:** If a statement says JE vaccine is not available, it would be incorrect because there are vaccines available for JE, such as the inactivated JE vaccine and live attenuated JE vaccine.
- **Option D:** If a statement claims JE only affects children, it would be incorrect because while JE can affect individuals of any age, it indeed has a higher incidence in children and older adults.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **Japanese encephalitis vaccine is recommended for travelers to endemic areas** and for residents of these areas, especially during outbreaks. The vaccine is usually administered in a series, and booster doses may be required for continued protection.

## Correct Answer: D.