Hepatitis C

　　The modes of transmission include parenteral transmission (parenteral transmission), similar to hepatitis B, and the main mode of transmission is blood and body fluids. People who have the habit of injecting drugs or substances (such as sharing needles) are usually at high risk of getting hepatitis C, with about 70% of infected individuals having a history of injecting drugs. Using unclean instruments for tattooing and piercing is also a risk factor. With the advancement of blood screening, the risk of post-transfusion HCV infection in developing countries has greatly decreased. In addition, in a statistical study in the United States, the chance of donating blood and testing positive for HCV after all blood tests is one in 10 million. In addition to blood transmission, HCV can also be transmitted through sexual contact and vertical transmission. The presence of HCV virus can be found in the seminal fluid and vaginal secretions of HCV infected individuals, and there are also some reports showing that sexual contact can transmit HCV. In addition, the opportunity for vertical transmission of HCV (transmitted from mother to the unborn child) is also very low, accounting for about 0% to 12%. To date, as high as 40% of infected individuals are infected for unknown reasons, so it seems that there are still unknown transmission routes.

　　What complications can hepatitis C easily lead to?

　　1. The incubation period of hepatitis C is from two to six months. After initial infection, about 80% of people will not show any symptoms. Possible acute symptoms include fever, general fatigue, decreased appetite, nausea, vomiting, abdominal pain, dark urine, light-colored stools, joint pain, and jaundice (yellowing of the skin and eyes).

　　2. Approximately 75-85% of new infections lead to chronic liver disease, and 60-70% of chronic carriers will develop chronic liver disease, 5-20% will develop liver cirrhosis, and 1-5% will die of liver cirrhosis or liver cancer. Hepatitis C is a carcinogen in 25% of liver cancer patients.

　　Hepatitis C does not always require treatment. The hepatitis C virus has six genotypes, and different genotypes may respond differently to treatment. Therefore, a careful screening is needed before treatment to determine the most appropriate treatment plan.

　　1. The combination therapy of interferon and ribavirin is the main method for treating hepatitis C at present. However, interferon is not universally available worldwide and is not always well tolerated. Some viral genotypes respond better to interferon than others, and many people who receive interferon treatment do not complete their course. As a result, although it is generally believed that hepatitis C is curable, many people have not been cured.

　　2. With the advancement of science, various new antiviral drugs for hepatitis C have been developed, which may be more effective than existing therapies and better tolerated. Telaprevir and boceprevir, two new therapeutic drugs, have recently been approved in some countries. A lot of work still needs to be done to ensure that more infected people worldwide can be treated after these advances.

　　3. Currently, there is no vaccine to prevent hepatitis C. You can reduce the risk of infection by avoiding the following behaviors:

　　(1) Unnecessary and unsafe injections.

　　(2) Unsafe blood products.

　　(3) Unsafe collection and disposal of sharp waste.

　　(4) Using illegal drugs and sharing needles.

　　(5) Unprotected sexual contact with HCV infected individuals.

　　(6) Sharing personal sharp items that may be contaminated with infected blood.

　　(7) Using contaminated tools for tattooing, piercing, and acupuncture.

　　4. The World Health Organization recommends that HCV infected individuals should:

　　(1) Receiving education and consultation on health care and treatment plans.

　　(2) Vaccination against hepatitis A and B to prevent simultaneous infection with hepatitis A and B viruses, in order to protect the liver.

　　(3) Early acceptance of appropriate medical management, including receiving appropriate antiviral treatment; and regular checks to enable early diagnosis of chronic liver disease.

　　Clinical significance of anti-HCV and HCV-RNA detection

　　1. Anti-HCV

　　1. Most HCV infected individuals have anti-HCV in their bodies. Therefore, detecting anti-HCV is very valuable for the diagnosis of hepatitis C. A positive anti-HCV is a marker for HCV infection. However, the current test results cannot fully reflect acute, chronic, or recovery phase infection. The antibody titer also cannot reflect the intensity of HCV infection, at least it has not been confirmed in animal experiments. A positive anti-HCV may indicate the immune status after recent infection, but most cases represent current HCV infection, and to some extent, reflect the individual's infectivity. The time from HCV infection to the positive conversion of anti-HCV varies greatly among individuals. Currently, the methods used to detect antibodies are late, and during this period, the only infection marker in patients is the absence of anti-RNA. In addition, 20% of hepatitis C patients never show anti-HCV, so the actual infection rate is higher than the detection rate, and a negative anti-HCV cannot exclude HCV infection.

　　2. Post-transfusion hepatitis C is relatively clear. After human infection with HCV, there can be four manifestations: ①Passively receiving high-titer anti-HCV-positive blood, and anti-HCV becomes positive after blood transfusion, turning negative after 5 weeks. Then, anti-HCV autoantibodies appear, which can remain positive; ②A delayed anti-HCV response that remains positive, generally turning positive after 20 to 22 weeks post-transfusion or 14 to 16 weeks post-onset of the disease, reaching a peak quickly and remaining positive for more than 10 years; ③A delayed short-term anti-HCV response, turning positive after 19 to 21 weeks post-transfusion or 9 to 11 weeks post-onset of the disease, turning negative after one year; ④No reaction, which is common in transient HCV infection, with anti-HCV always negative.

　　3. The detection of anti-HCV IgM is different from the reaction patterns of other viruses' IgM: ①IgM appears later than IgG; ②IgM exists for a long time, at least 3 to 8 years or even longer; ③The titer of IgM is positively correlated with that of IgG; ④There is a secondary IgM antibody response. It indicates that anti-HCV IgM cannot be used as an early diagnostic indicator for HCV infection, cannot distinguish between recent and past infections, but may reflect chronicization or viremia, and can be used as an indicator for prognosis and efficacy.

　　Second, HCV-RNA

　　Because the HCV content in the blood of hepatitis C patients is very low, it is difficult to detect HCV-RNA directly by nucleic acid hybridization, and it is necessary to amplify the nucleic acid first and then determine it. The determination of HCV RNA in liver and serum by semi-quantitative polymerase chain reaction (HCVcDNA/PCR, abbreviated as cPCR) has the advantages of strong specificity, high sensitivity, and rapidity. HCVRNA positivity is direct evidence of HCV infection, is a replication indicator of HCV, and is infectious. Since HCVRNA appears earlier than anti-HCV, it can be used for early diagnosis and screening of blood donors. HCVRNA negativity indicates that HCV has been cleared, and can also be used as an indicator of prognosis and efficacy.

　　So far, there is no effective immunization against hepatitis C, and the only preventive measure is to prevent blood contact. There is currently no vaccine or preventive treatment, but if the virus is detected within half a year after infection, a 24-week interferon therapy can cure hepatitis C in 90% of cases before the disease enters chronic phase.

　　1. Hepatitis C does not always require treatment. The hepatitis C virus has six genotypes, and different genotypes may have different responses to treatment. Therefore, careful screening is needed before starting treatment to determine the most appropriate treatment plan.

　　2. Interferon and ribavirin combination antiviral therapy is the main method for treating hepatitis C. However, interferon is not universally available worldwide and is not always well tolerated. Some viral genotypes respond better to interferon than others, and many people who use interferon for treatment do not complete their course. As a result, although it is generally believed that hepatitis C is curable, many people have not been cured.

　　With the advancement of science, a variety of new antiviral drugs for hepatitis C have been developed, which may be more effective than existing therapies and have better tolerance. Recently, some countries have approved telaprevir and boceprevir, these two new therapeutic drugs. A lot of work still needs to be done to ensure that more infected people worldwide can receive treatment after these advances.