Hepatitis C is a disease mainly transmitted through blood. Chronic infection with hepatitis C virus (HCV) can lead to chronic inflammatory necrosis and fibrosis of the liver, and some patients can develop cirrhosis or even hepatocellular carcinoma (HCC), which is extremely dangerous to the health and life of patients and has become a serious social and public health problem. With the support of the Ministry of Health and the leadership of the Chinese Medical Association, the Hepatology and Infectious and Parasitic Diseases Sections of the Chinese Medical Association organized domestic experts to develop guidelines for the prevention and treatment of hepatitis C in China in accordance with the principles of evidence-based medicine and the latest research results at home and abroad.
Etiology of hepatitis C
(A) Characteristics of HCV
HCV belongs to the family Flaviviridae, and its genome is single-stranded positive-stranded RNA, which is easily mutable and can be divided into six genotypes and different subtypes. Genotype 1 is globally distributed, accounting for more than 70% of all HCV infections. after HCV infects the host, after a certain period of time, a cluster of related mutant strains of viruses, mainly a dominant strain, is formed in the infected person, called quasispecies.
(B) HCV genome structural characteristics
The HCV genome contains an open reading frame (ORF) encoding more than 10 structural and non-structural (NS) proteins, NS3 protein is a multifunctional protein with protease activity at the amino terminus and helicase/nucleoside triphosphate activity at the carboxyl terminus; NS5B protein is an RNA-dependent RNA polymerase, both of which are necessary for HCV replication and are important targets for antiviral therapy.
(C) HCV inactivation methods
HCV is sensitive to general chemical disinfectants; 100°C for 5 min or 60°C for 10 h, high pressure steam and formaldehyde fumigation can inactivate the virus.
Epidemiology of hepatitis C
(A) World epidemiological status of hepatitis C
Hepatitis C is globally prevalent and is the most important cause of end-stage liver disease in countries such as Europe, the United States and Japan. According to the World Health Organization, the global infection rate of HCV is about 3%, and it is estimated that about 170 million people are infected with HCV, with about 30,000 to 50,000 new cases of hepatitis C each year.
(B) The epidemiological situation of hepatitis C in China
The national sero-epidemiological survey data show that the rate of anti-HCV positivity in the general population in China is 3.2%. The anti-HCV positivity rate varies from place to place and increases gradually with age, from 2.0% in the age group of 1 year to 3.9% in the age group of 50-59 years. HCV genotypes 1b and 2a are more common in China, with type 1b predominant; types 1a, 2b and 3b have been reported in some areas; type 6 is mainly seen in Hong Kong and Macau, and this genotype can also be seen in the southern border provinces.
(C) Hepatitis C transmission route
1, HCV is mainly transmitted through blood, mainly.
(1) Transmission by 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, unstable quality of anti-HCV testing reagents and the fact that a few infected patients do not produce anti-HCV, it is not possible to completely screen out HCV-positive people, 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 90% of transmission in some areas. The use of non-disposable syringes and needles, dental instruments that are not strictly sterilized, endoscopy, invasive procedures, and needle sticks 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 earring 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 a higher risk of HCV infection. People 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%, and 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%. high HCV viral load may increase the risk of transmission.
The route of transmission for 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.
Natural history of hepatitis C
HCV RNA can be detected in peripheral blood 1 to 3 weeks after exposure to HCV, but only 50% to 70% of patients are anti-HCV positive at the time of clinical symptoms in acute HCV-infected patients, and about 90% of patients are anti-HCV positive after 3 months.
After HCV infection, those whose viremia persists for 6 months and is not cleared are chronically infected, and the rate of chronicity of hepatitis C is 50% to 85%. The incidence of cirrhosis is 2% to 94% in children and young women 20 years after infection; 20% to 30% in middle-aged people infected by blood transfusion; and 10% to 15% in the general population. spontaneous clearance of the virus is higher in people under 40 years of age and in women infected with HCV; the progression of the disease can be promoted by those who are over 40 years of age at the time of HCV infection, men and those co-infected with HIV and resulting in immunocompromise. 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 due to environmental pollution can also promote disease progression.
The incidence of HCV-associated HCC is 1% to 3% after 30 years of infection and is seen mainly in patients with cirrhosis and progressive liver fibrosis, and once it develops into cirrhosis, the annual incidence of HCC is 1% to 7%. The above-mentioned factors that promote the progression of hepatitis C, as well as diabetes mellitus, can contribute to the development of HCC. The incidence of HCC is relatively high in patients with hepatitis C after blood transfusion. Patients who develop cirrhosis and HCC both have a reduced quality of life.
Cirrhosis and HCC are the main causes of death in patients with chronic hepatitis C, with decompensated cirrhosis being the most predominant. It has been reported that once cirrhosis occurs, the 10-year survival rate is about 80%, and if decompensation occurs, the 10-year survival rate is only 25%. The incidence of HCC in complete responders after interferon (IFNα) therapy (including those who relapse after complete response); is low, but the incidence of HCC in non-responders is high.
Prevention of HCV transmission
(A) Hepatitis C vaccine prevention
There is no effective vaccine to prevent hepatitis C.
(B) Strict screening of blood donors
Strictly implement the Blood Donation Law of the People’s Republic of China and promote blood donation without compensation. Strictly screen blood donors by testing serum anti-HCV and alanine aminotransferase (ALT). Detection methods for HCV antigens should be developed to improve the detection rate of those infected during the window period.
(C) Prevention of transdermal and mucosal route transmission
Promote safe injection. Medical instruments such as dental instruments and endoscopes should be strictly disinfected. Medical personnel should wear gloves when touching patients’ blood and body fluids. Provide psychological counseling and safety education to intravenous drug users to persuade them to quit drugs. Do not share razors and dental instruments, etc. Haircutting appliances, piercing and tattooing appliances should be strictly disinfected.
(iv) Prevention of sexual transmission
People with a history of sexual promiscuity should be examined regularly and management should be strengthened. It is recommended that HCV-infected persons use condoms during sexual intercourse. Proper sex education should be provided to adolescents.
(E) Prevention of mother-to-child transmission
For HCV RNA-positive pregnant women, amniocentesis should be avoided to minimize the delivery time, ensure the integrity of the placenta and reduce the exposure of the newborn to maternal blood.