Staphylococcus aureus (S. aureus or “staph”) facts, including how S. aureus is spread, common symptoms and complications. S. aureus has long been recognized as one of the most important bacteria that cause disease in humans.lthough most staph infections are not serious, S. aureus can cause serious infections such as bloodstream infections, pneumonia, or bone and joint infections. On this page: Signs and symptoms of infection. Duration of illness. Transmission.