Fungal infections today are among the most difficult diseases to manage in humans. Some fungi cause disease in healthy people, but most fungal infections occur in individuals already experiencing serious illness, and frequently jeopardize the success of the newest medical advances in cancer care, solid organ and hematopoietic stem cell transplantation, neonatal medicine, autoimmune disease therapies, trauma and intensive care, and sophisticated surgery. In fact, these medical advances themselves often make their beneficiaries vulnerable to fungal disease. Treatment can involve breaching normal immune functions, or susceptible patients, such as extremely premature newborns who survive long enough to become infected by a fungus.