Varicella (chickenpox) is a virus that spreads easily among people by coughing or sneezing. It incubates in the body for 14–16 days, then causes a very itchy rash. Blisters usually begin on the scalp or face and spread down to the trunk. Besides causing discomfort, the blisters can become infected and cause scarring. Sometimes varicella infection can be serious or life threatening. Although serious infection is rare, it can cause pneumonia, brain swelling, and death.
The risk of serious infection increases with age. Adolescents, adults, and people with certain high-risk conditions typically have more severe cases of disease.