Streptococcus pyogenes can cause both invasive diseases (such as meningitis or bloodstream infections) and non-invasive diseases (such as strep throat). Only invasive disease is reportable to the Texas Department of State Health Services. Non-invasive illness may result in strep throat or a skin infection such as impetigo. Group A streptococcus infections can also begin as a non-invasive infection and then spread to parts of the body where bacteria are not normally found, like the blood or muscle tissue. When the bacteria get into these parts of the body the infections are called invasive. Two of the most severe kinds of invasive Group A streptococcus infections are necrotizing fasciitis and streptococcal toxic shock syndrome. In necrotizing fasciitis, the bacteria destroy muscle, fat, and skin tissue and because of this it has been described as "flesh-eating bacteria." Streptococcal toxic shock syndrome is an infection that moves quickly, causing shock and internal organs such as the kidneys, liver, and lungs to fail. Both necrotizing fasciitis and streptococcal toxic shock syndrome are rare.
Very few people who come in contact with Group A streptococcus will develop invasive disease. Most people, if they get sick, will have a throat or skin infection, and some people may have no symptoms at all. Although healthy people can get Group A streptococcus invasive disease, people with chronic illnesses like cancer, diabetes, and chronic heart or lung disease, and those who use medications such as steroids have a higher risk. Persons with skin lesions (such as cuts, chicken pox, and surgical wounds), the elderly, and adults with a history of alcohol abuse or injection drug use also have a higher risk for disease.