Herpes zoster, commonly known as shingles, is a viral infection caused by the reactivation of the varicella-zoster virus, which also causes chickenpox. After a person recovers from chickenpox, the virus remains dormant in the nervous system and can reactivate later in life, leading to shingles. Symptoms typically include a painful rash that develops on one side of the body, often accompanied by fever and fatigue. The rash usually appears as blisters that eventually crust over and heal within a few weeks. Shingles can occur at any age but is more common in older adults and those with weakened immune systems. Vaccines are available to help reduce the risk of developing shingles and its complications.