**Core Concept**
The patient's symptoms of headache, fever, and neck stiffness, combined with a normal physical examination and no focal neurologic signs, are suggestive of a viral meningitis. This condition is characterized by inflammation of the protective membranes covering the brain and spinal cord, known as the meninges.

**Why the Correct Answer is Right**
The most common cause of viral meningitis is enteroviruses, which are highly contagious and often spread through fecal-oral transmission. These viruses can enter the body through contaminated food or water, or by direct contact with an infected person. The symptoms of viral meningitis, such as headache and neck stiffness, are caused by the inflammatory response to the viral infection. The absence of focal neurologic signs and the normal physical examination support the diagnosis of viral meningitis rather than bacterial meningitis, which would typically present with more severe symptoms and signs.

**Why Each Wrong Option is Incorrect**
**Option A:** Herpes simplex virus (HSV) is not the most common cause of viral meningitis, although it can cause meningitis, particularly in immunocompromised individuals. HSV typically presents with more severe symptoms and signs, such as focal neurologic deficits and a more pronounced inflammatory response.

**Option B:** Arboviruses, such as West Nile virus, can cause meningitis, but they are less common in this population and would typically be associated with a more severe clinical presentation.

**Option C:** Listeria monocytogenes is a rare cause of meningitis, typically seen in immunocompromised individuals, such as pregnant women, the elderly, and those with chronic medical conditions.

**Option D:** Tuberculous meningitis is a rare cause of meningitis, typically seen in individuals with a history of tuberculosis or exposure to someone with TB.

**Clinical Pearl / High-Yield Fact**
In cases of suspected viral meningitis, it is essential to obtain a thorough history, including recent travel, exposure to sick contacts, and contaminated food or water. A lumbar puncture (LP) should be performed to collect cerebrospinal fluid (CSF) for analysis, which may include culture, PCR, and other diagnostic tests to confirm the diagnosis.

**Correct Answer:** D.