Chickenpox is a viral infection in which a person develops extremely itchy blisters all over the body. It used to be one of the classic childhood diseases. However, it has become much less common since the introduction of the chickenpox vaccine.
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 can be spread very easily to others. You may get chickenpox from touching the fluids from a chickenpox blister, or if someone with the disease coughs or sneezes near you. Even those with mild illness may be contagious.