What are the causes of shingles?

Cause of shingles

Shingles is caused by an activation of the varicella-zoster virus. After a patient is infected with chickenpox, the immune system develops antibodies to protect against the virus. However, the virus remains in the dorsal root ganglia (spinal nerve cells). Reactivation of the virus usually develops in adults over age 50 as a result of naturally declining immunity to the virus. The virus can also be reactivated in some cancer, transplant, or AIDS patients.