Chickenpox is caused by the varicella-zoster virus, a member of the herpesvirus family. The same virus also causes herpes zoster, shingles, in adults. Chickenpox is extremely contagious, and can be spread by direct contact, droplet transmission, and airborne transmission. Symptoms range from fever, headache, stomach ache, or loss of appetite before breaking out in the classic pox rash. The rash can consist of several hundred small, itchy, fluid-filled blisters over red spots on the skin. The blisters often appear first on the face, trunk, or scalp and then spread to other parts of the body.Update Date: 6/19/2008 Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.