A childhood infection causing an itchy, blister-like rash that can be prevented by a vaccine.

Chickenpox is caused by the varicella-zoster virus. It spreads easily to people who haven't had chickenpox or the chickenpox vaccine. Chickenpox is often a mild disease. But it can be serious and lead to other health problems. This illness can be prevented by the chickenpox vaccine.

Chickenpox symptoms include fever, not wanting to eat, headache and tiredness. About 10 to 21 days after contact with the chickenpox virus, an itchy rash appears. At first it looks like raised bumps. Then the bumps fill with fluid like blisters, which break, crust and scab over.

Chickenpox often needs no medical treatment. Some people may take medicine to calm the itchiness of the rash. For people at high risk of serious illness or other health problems, antiviral medicine may be given.