According to Mayo Clinic, shingles is caused by the same virus that causes chickenpox known as the varicella-zoster virus. The virus typically remains dormant in the nervous system for years until it eventually reactivates and produces the symptoms. As an individual's immune system weakens, it becomes more likely that they will develop shingles if they have previously had chickenpox. If you believe you may be experiencing symptoms, contact your doctor immediately to learn your next steps.