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Chickenpox (varicella) is a common contagious illness that is caused by a type of herpes virus.

Chickenpox is most common in children and is usually not serious. In teenagers, adults, pregnant women, and people who have impaired immune systems, chickenpox can be more serious.

Symptoms include a fever, a generally ill feeling, and the development of a widely scattered, itching rash with fluid-filled blisters. The blisters break open and crust over after several days. New blisters continue to develop for up to a week.

Treatment for chickenpox focuses on relieving fever and discomfort. A vaccine to prevent chickenpox is available and is recommended for children and for teens and adults who did not have chickenpox in childhood.