Shingles and chickenpox were once considered separate disorders. Researchers now know that they are both caused by a single virus of the herpes family, known as varicella-zoster virus (VZV). The word herpes is derived from the Greek word "herpein," which means "to creep," a reference to a characteristic pattern of skin eruptions.

VZV is still referred to by separate terms:

Varicella: The primary infection that causes chickenpox
Herpes zoster: The reactivation of the virus that causes shingles