Model released. Child affected by varicella, also known as chickenpox, taking paracetamol to reduce fever. It is an infectious disease of childhood characterised by a rash and slight fever. It is caused by an herpesvirus which is transmitted by airborne droplets. After an incubation period of 11-18 days a mild fever develops followed by an itchy rash of dark red pimples which spread from the trunk to the face, scalp and limbs. The pimples develop into blisters and then scabs which drop off after about 12 days. The only treatment is bed rest and the application of calamine lotion relieves the itchiness of the rash. If it occurs in adults it usually takes a more severe form.