Varicella, commonly known as chickenpox, is a highly contagious disease caused by the varicella-zoster virus (VZV). It typically causes an itchy, blister-like rash that starts on the chest, back, and face before spreading, along with fever, fatigue, and loss of appetite. The illness is usually mild in children but can be more severe in infants, adults, pregnant women, and immunocompromised individuals. It spreads through respiratory droplets or direct contact with fluid from the rash. Vaccination with the varicella vaccine is highly effective at preventing infection or reducing severity if contracted.