The cause of shingles is which virus?

• A. cytomegalovirus
• B. Rubella virus
• C. Varicella-zoster virus
• D. HTLV-I

Answer: (C)

Shingles is caused by reactivation of Varicella-zoster virus, the herpesvirus that originally causes chickenpox. After the initial infection, the virus stays latent in sensory nerve ganglia, especially the dorsal root or trigeminal ganglia. Later in life, or when the immune system is weakened, the virus can reactivate and travel along a nerve to the skin, producing a painful, vesicular rash that typically runs in a single dermatome. This reactivation mechanism distinguishes shingles from the other viruses listed, which cause different diseases (for example, CMV can cause congenital or mononucleosis-like illness, rubella causes German measles, and HTLV-I is linked to other conditions).