The medical name for chicken pox. An acute, communicable, infectious disease, usually contracted by young children. Chicken pox is caused by the varicella virus. The infection is characterized by a fever and itchy red spots. They usually appear on the chest and stomach first, then appear in crops over the entire body. The red spots turn into small blisters that dry up and form scabs over about a week. They occasionally cause scarring, particularly if scratched or if they become infected with bacteria. A varicella vaccine, available since 1995, has significantly reduced the number of cases of varicella in the US.