Chickenpox is usually acquired through inhalation of airborne respiratory droplets from an infected host. High viral titers are found in the characteristic vesicles of chickenpox; viral transmission may also occur through direct contact with these vesicles, though the risk of transmission is lower.
Chickenpox is largely a childhood disease, with more than 90% of cases occurring in children younger than 10 years. The disease is benign in the healthy child, and increased morbidity occurs in adults and immunocompromised patients. An outbreak of varicella was noted in a group of lymphoma patients treated with rituximab and was related to exposure to a patient with zoster.