Chickenpox to Shingles: Where the Virus Hides and Reactivates

After chickenpox (primary varicella-zoster virus infection), VZV establishes lifelong latency in sensory ganglia—not the spinal cord itself.

Latency Sites

• Cranial nerve ganglia: Trigeminal (most common for shingles), geniculate, vestibular
• Dorsal root ganglia (DRG): Thoracic (T3–L2 most common), cervical, lumbar, sacral
• Autonomic ganglia: Less common

Reactivation Pathway

1. VZV reactivates in ganglion (trigger: aging, immunosuppression, stress, trauma)
2. Viral replication → anterograde transport along sensory nerve axons
3. Reaches cutaneous nerve endings → dermatomal rash
4. Inflammatory response → pain, vesicles, erythema

Key Clarifications

• ❌ Not "retreats to spinal cord" — resides in ganglia (nerve cell bodies) adjacent to cord
• ❌ Not in bloodstream during latency
• ✅ Dermatomal distribution reflects ganglion innervation territory
• ✅ Thoracic > cervical > lumbar > sacral > cranial (frequency)

Clinical Implications

• Shingles (herpes zoster): Unilateral dermatomal vesicles + pain
• Postherpetic neuralgia (PHN): Pain >90 days after rash; risk ↑ with age
• Complications: Ophthalmicus (V1), Ramsay Hunt (geniculate), myelitis, encephalitis
• Vaccination: Shingrix (RZV) 2 doses ≥50 yrs — >90% efficacy; Zostavax (live) discontinued US

The virus hides in nerve cell bodies (ganglia), not the spinal cord proper. Reactivation follows sensory nerves to skin.