Varicella (chickenpox) is a disease caused by infection with the varicella zoster virus, which causes fever and an itchy rash.

Symptoms of varicella include a skin rash of blister-like lesions, covering the body but usually more concentrated on the face, scalp, and trunk. Most, but not all, infected individuals have fever, which develops just before or when the rash appears. If exposed, persons who have been vaccinated against the disease may get a milder illness, with less severe rash (sometimes involving only a few red bumps that look similar to insect bites) and mild or no fever.

Varicella is spread by coughing and sneezing (highly contagious), by direct contact, and by aerosolization of virus from skin lesions.