It can be secondary to pneumococcal pneumonia, otitis media, mastoiditis, and pharyngitis. The bacteria mostly enter the blood from the lungs through the thoracic duct via the drainage lymphatic pathway. In otitis media and mastoiditis, pneumococcus can enter the blood through the venous sinuses. 20% to 30% of patients with pneumococcal pneumonia have positive blood cultures, and the positive rate increases with age. Type II pneumococcal pneumonia is more likely to cause it. It occurs more frequently in patients who have undergone splenectomy, which may be related to the fact that the mononuclear phagocyte system of the spleen has a powerful function of phagocytizing and killing encapsulated pneumococci. Patients with other existing serious diseases such as sickle cell anemia and immunodeficiency are prone to pneumococcal sepsis.