Which virus is responsible for causing shingles?

The Varicella-zoster virus is the correct answer because it is the virus that causes both chickenpox (varicella) and shingles (herpes zoster). Once a person has had chickenpox, the virus remains dormant in the sensory nerve ganglia. Later in life, often when the immune system is weakened due to stress, age, or illness, the virus can reactivate, leading to shingles. Shingles typically presents with a painful rash that follows a dermatomal distribution, as it affects the nerves where the virus had been dormant.

The other viruses listed have distinct roles: the herpes simplex virus primarily causes oral and genital herpes, cytomegalovirus is associated with various infectious diseases and complications particularly in immunocompromised individuals, and Epstein-Barr virus is known for its link to mononucleosis and certain cancers but does not cause shingles. Therefore, that makes Varicella-zoster virus the definitive causative agent of shingles.