Subacute infective endocarditis often occurs on the basis of heart diseases such as rheumatic heart valve disease, ventricular septal defect, and patent ductus arteriosus. It can also occur in people without heart disease. The pathogens are mainly bacteria, followed by fungi, rickettsia, chlamydia and viruses. The main manifestations are low-to-moderate fever, progressive anemia, fatigue, night sweats, hepatosplenomegaly, clubbing of fingers (toes), and vascular embolism. There are more young and middle-aged patients. In recent years, it has been found that the incidence of this disease has increased after mitral valve prolapse, cardiac catheterization and heart surgery, and senile valvular degeneration, and the age of onset has gradually increased. Grass-green streptococci are the main pathogens of the disease, but they have been significantly reduced in recent years. Various staphylococci, hemolytic streptococci, enterococci and gram-negative bacteria have become the main pathogens.