Final answer:
In shingles, the vesicles are unilateral, appearing on one side of the body. They occur when the varicella-zoster virus, which initially causes chickenpox, is reactivated. Shingles is not directly transmissible between individuals.
Step-by-step explanation:
The vesicles in shingles are typically unilateral. This means they appear on only one side of the body or face. The reason for this is that the varicella-zoster virus (VZV), which causes both chickenpox and shingles, becomes dormant in nerve cell ganglia after an initial chickenpox infection. When reactivated, usually due to triggers such as stress, aging, or immunosuppression, VZV travels along the sensory nerves to the skin, resulting in the characteristic painful rash of shingles.
Shingles can result in complications such as postherpetic neuralgia, where pain persists in the area of the rash long after other symptoms have subsided. It's important to note that while a person with active shingles can transmit the VZV to someone who has never had chickenpox, causing them to develop chickenpox, shingles itself is not directly transmissible between individuals.