Chicken pox (Varicella) is a highly communicable viral disease caused by the varicella-zoster virus.Varicella is a member of the herpes family, and, like all herpes viruses, stays in the body for life once acquired. It is uncommon to get chicken pox more than once.hicken pox (Varicella) is a highly communicable viral disease caused by the varicella-zoster virus.