Varicella zoster is a virus. It causes chickenpox, also called varicella and shingles, called herpes zoster. After the chickenpox runs its course, the virus retreats to nerve tissues near your spinal cord and brain, where it hides out.

Doctors don’t know why, but sometimes the virus wakes up and travels along nerve fibers to your skin and causes shingles. Chickenpox, also called varicella, is characterized by itchy red blisters that appear all over the body. A virus causes this condition. It often affects children, and was so common it was considered a childhood rite of passage.

It’s very rare to have the chickenpox infection more than once. And since the chickenpox vaccine was introduced in the mid-1990s, cases have declined.