Type II infection: This infection accounts for 20 to 30% of cases, mainly involving the extremities. This mainly involves "Streptococcus pyogenes" bacteria, alone or in combination with staphylococcal infections. Both types of bacteria can progress rapidly and manifest as toxic shock syndrome. "Streptococcus" species produce M protein, which acts as a superantigen, stimulating a massive systemic immune response which is not effective against the bacterial antigen, precipitating shock. Type II infection more commonly affects young, healthy adults with a history of injury.