Chicken pox is caused by Human Herpes Virus Type 3, also known as the varicella-zoster virus. There are eight herpes subtypes that each have different health implications - classically, type 1 & 2 are sexually transmitted but types 4 and 5 (which are the causes of good ol' fashion mono can be transmitted through saliva). When you're infected with the virus as a child (chickenpox) your body will develop immunity to it and the virus will retreat into the nerve cells in your back. Each of these nerve cells supply the sensation to bands of skin called "dermatomes" that warp around your torso and chest. Later in life the virus can reactivate in times of stress or depressed immunity and travel away to the ends of these nerves close to the surface of the skin where they erupt into painful blistering lesions we call zoster, or Shingles. The band-like pattern the lesions appear on indicates which spinal nerve the virus was hiding in. By the way, there's a vaccine for shingles that may be given to adults over 60 years old and some over 50, and you don't need to have a history of chicken pox or shingles to receive it.