1.Blood transmission, mainly: (1)Transmission by blood transfusion and blood products. This route has been effectively controlled in China since 1993 when blood donors were screened for anti-HCV. 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 RN A-positive individuals, and there is still a possibility of HCV infection from massive blood transfusion and hemodialysis. (2) Transmission via broken skin and mucous membranes This is by far the predominant mode of transmission, with HCV transmission due to intravenous drug use accounting for 60% to 9 0% in some areas. The use of non-disposable syringes and needles, non-sterile dental instruments, endoscopy, invasive procedures and needlesticks are also important routes of transmission through the skin and mucous membranes. 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 HCV transmission via blood. 2. Sexual transmission: People who have sexual intercourse with HCV-infected persons and those who have sexual promiscuity have a higher risk of contracting HCV. People with other sexually transmitted diseases, especially those infected with human immunodeficiency virus (HIV), have a higher risk of HCV infection. The risk of 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%; the risk of transmission increases to 20% when HIV infection is combined. 4. The transmission route of some HCV infected patients is unknown. HCV is not generally transmitted by kissing, hugging, sneezing, coughing, food, drinking water, sharing utensils and cups, no skin breaks and other non-blood-exposed contacts. HCV infection is chronic if the viremia persists for 6 months after infection, and the chronicity rate of hepatitis C is 50%-85%. The incidence of cirrhosis 20 years after infection is 2% to 4% in children and young women, 20% to 30% in middle-aged people infected by blood transfusion, and 10% to 15% in the general population; the rate of spontaneous clearance of HCV infection is higher in people under 40 years of age and in women; HCV infection in men over 40 years of age and co-infection with HIV that leads to immunocompromise may promote disease progression. Co-infection with hepatitis B virus (HBV), alcoholism (50 g/d or more), non-alcoholic fatty liver disease (NASH), high iron load in the liver, co-infection with schistosomes, hepatotoxic drugs, and toxic substances from environmental pollution may also contribute to disease progression. The incidence of HCV-associated HCC ranges from 1% to 3% after 30 years of infection, mainly in patients with cirrhosis and progressive liver fibrosis, and once cirrhosis has developed, the annual incidence of HCC is 1% to 7%. The above factors that promote the progression of hepatitis C, as well as diabetes, can contribute to the development of HCC. The incidence of HCC is relatively high in patients with hepatitis C after blood transfusion. The quality of life of patients with cirrhosis and HCC is reduced.