Chickenpox (Varicella) By Kenneth M Kaye, MD, Harvard Medical School Reviewed / Revised Sep 2021 | Modified Sep 2022 View Patient Education Symptoms and Signs Diagnosis Prognosis Treatment Prevention Key Points More Information Topic Resources Chickenpox (Back) Chickenpox (Face) Chickenpox is an acute, systemic, usually childhood infection caused by the varicella-zoster virus (human herpesvirus type 3).