**Core Concept**
Mumps is a viral infection caused by the mumps virus (MuV), leading to inflammation of the salivary glands, particularly the parotids. This illness can manifest with a range of symptoms, from mild to severe, and can involve various organs and systems in the body.

**Why the Correct Answer is Right**
Menigoencephalitis is a rare but serious complication of mumps, characterized by inflammation of the meninges and brain. This condition typically occurs before the onset of parotitis (parotid gland inflammation), which is the hallmark symptom of mumps. The exact mechanism behind this phenomenon is not fully understood, but it is believed to be related to the virus's ability to cause inflammation and damage to the central nervous system. The meningoencephalitis can be triggered by the MuV's effect on the immune system, leading to an overactive response that results in inflammation of the meninges and brain.

**Why Each Wrong Option is Incorrect**
**Option A:** Salivary gland involvement in mumps is not limited to the parotids. In addition to the parotid glands, the submandibular and sublingual glands can also be affected, leading to a range of symptoms, including swelling, pain, and difficulty swallowing.

**Option B:** Patients with mumps are typically infectious before the onset of clinical parotid enlargement. The MuV can be shed in the saliva and mucus of infected individuals for several days before symptoms appear, making it essential to practice good hygiene and take precautions to prevent transmission.

**Option D:** Mumps orchitis, which occurs in post-pubescent males, can lead to testicular atrophy and infertility in some cases. However, this is a rare complication, and the majority of individuals who develop orchitis do not experience long-term consequences.

**Clinical Pearl / High-Yield Fact**
Mumps can be prevented through vaccination, and the MMR (measles, mumps, and rubella) vaccine is highly effective in preventing the disease. It is essential for healthcare professionals to remain vigilant and provide accurate information to patients about the risks and benefits of vaccination.

**✓ Correct Answer: C. Menigoencephalitis can precede parotitis**