Group A streptococcal disease (GAS) is caused by a bacterium (germ) called Streptococcus pyogenes,group A. People may carry the germ on their skin or in their noses and throats and have no symptoms of illness. Most often, Group A streptococcal infections are mild illnesses such as “strep throat” or impetigo. Sometimes, the bacteria invade the lungs (pneumonia), blood (septicemia), or spread along the layers of tissue that surround muscle (called the fascia). These infections are called invasive Group A streptococcal (iGAS) disease and are very serious, even life-threatening.
Two of the most severe, but least common, forms of iGAS are necrotizing fasciitis and streptococcal toxic shock syndrome. Necrotizing fasciitis, also known as "flesh-eating disease," is a rapidly progressing disease which destroys muscles, fat, and skin tissue. Streptococcal toxic shock syndrome results in a rapid drop in blood pressure and causes organs such as the kidneys, liver, or lungs to stop working.