Shingles occurs
**Core Concept**
Reactivation of varicella-zoster virus (VZV) causes shingles, also known as herpes zoster. This occurs when the latent virus, initially acquired during childhood chickenpox, reactivates and travels along the sensory nerve ganglia.
**Why the Correct Answer is Right**
The varicella-zoster virus resides in the dorsal root ganglia of the spinal nerves, where it remains dormant for years. Reactivation of the virus leads to inflammation of the nerve, causing pain and a characteristic rash along the dermatome innervated by the affected nerve. This is because the virus travels down the axons of the nerve to the skin, causing the characteristic vesicular rash. The rash typically appears as a band or strip on one side of the body, following the distribution of the affected nerve.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because shingles does not occur due to a new infection with varicella-zoster virus. It's a reactivation of a latent virus.
**Option B:** Incorrect because shingles can occur in anyone who has had chickenpox, not just immunocompromised individuals.
**Option C:** Incorrect because shingles is not primarily caused by an allergic reaction to the virus.
**Clinical Pearl / High-Yield Fact**
The varicella-zoster virus can reactivate at any age, but the risk increases with age, especially after 60 years.
**Correct Answer: B. Anyone who has had chickenpox is at risk of developing shingles.**