1.Blood transmission: It is the main transmission route of HCV, mainly: (1) Transmission through blood transfusion and blood products. This route has been effectively controlled since 1993 when blood donors were screened for anti-HCV in China. However, due to the existence of window period of anti-HCV, the unstable quality of anti-HCV testing reagents and the fact that a small number of infected patients do not produce anti-HCV, it is not possible to completely screen out HCV RNA-positive people, and there is still a possibility of HCV infection through massive blood transfusion and hemodialysis.(2) Transmission through broken skin and mucous membranes. This is by far the predominant mode of transmission, and in some areas, HCV transmission due to intravenous drug use accounts for 60% to 90%. The use of non-disposable syringes and needles, dental instruments not strictly sterilized, endoscopy, invasive manipulation and needlesticks are also important routes of transdermal transmission. Some traditional medical practices that may lead to skin breakdown and blood exposure are also associated with HCV transmission; sharing razors, toothbrushes, tattoos, and ear piercing are also potential modes of transmural transmission of HCV. 2.Sexual transmission: People who have sexual intercourse with HCV-infected people and those who have sexual promiscuity have higher risk of HCV infection. Those with other sexually transmitted diseases, especially those infected with human immunodeficiency virus (HIV), have a higher risk of HCV infection. 3. Mother-to-child transmission: The risk of HCV transmission from an anti-HCV-positive mother to her newborn is 2%, but if the mother is positive for HCV RNA at the time of delivery, the risk of transmission can be as high as 4% to 7%; when combined with HIV infection, the risk of transmission increases to 20%. A high HCV viral load may increase the risk of transmission. The route of transmission in some HCV-infected patients is unknown. Kissing, hugging, sneezing, coughing, food, drinking, sharing utensils and glasses, no skin breaks and other non-blood-exposed contacts generally do not transmit HCV.