Scarlet fever rash on a patient's back. Scarlet fever (or scarlatina) is a disease which mainly affects children. It is caused by Streptococcus bacteria. It is highly contagious, and is spread in droplets of fluid coughed, sneezed or breathed into the air. Symptoms occur 2-4 days after exposure and include fever, sore throat and a widespread red rash affecting the torso, limbs and tongue. The rash is caused by a toxin released by the bacteria. Treatment is with antibiotic drugs such as penicillin, which usually leads to a rapid recovery. Infection confers life-long immunity.