At present, the number of patients infected with viral hepatitis B (HBV) has exceeded 300 million worldwide, and about one million people die from viral hepatitis every year. In China, the number of chronic hepatitis B virus carriers has reached about 130 million people, and there are 30 million chronic hepatitis B patients. In our daily life, we often find some people who are negative for hepatitis B surface antigen but positive for anti-HBc. Studies have found that the detection rate of single anti-HBc positive people in the general population in different parts of the world varies from 5% to 20.0%, and the difference in detection rate may be related to the high rate of hepatitis B infection and testing methods in different countries and regions. So what does a single positive anti-HBc mean? First: chronic hepatitis B infection: some single anti-HBc positive people, especially those with high levels of anti-HBc positivity, still have hepatitis B virus replication in their bodies, but because of the low level of hepatitis B virus replication, it is not easy to detect by conventional methods. However, they can be found to be positive for hepatitis B virus DNA when tested by sensitive hepatitis B virus nucleic acid amplification method. Therefore, when the body resistance or immune function decreases, the hepatitis B virus replication is rapidly enhanced and they can evolve into typical hepatitis B. Post-transfusion hepatitis B has been reported both at home and abroad in some non-hepatitis patients due to blood transfusion from a single anti-HBc positive blood donor, or hepatitis B virus reinfection due to transplantation of organs provided by anti-HBC positive persons, etc. Therefore, for patients receiving blood transfusions, there will be a high risk of hepatitis B infection with such blood transfusions. Second: A single positive anti-HBc may also be a “window period” Acute hepatitis B infection: HBsAg (hepatitis B surface antigen) has disappeared while anti-HBc is present. Third: past hepatitis B infection: a manifestation of recovery from hepatitis B infection, which may be due to the presence of HBV in the body and the replicative expression of HBeAg (hepatitis B e antigen) below the limit of conventional detection. Therefore, some people believe that a single positive anti-HBc is a low level of hepatitis B virus carrier with undetectable HBs-Ag in the blood, which is the result of an occult infection. Fourth: Other causes. In short, when single anti-HBc antibody positive after antibody infection with HBV, you should pay frequent attention to your liver function, regular testing and follow-up, and develop a healthy liver protection program suitable for yourself under the guidance of a professional doctor, and anti-HBc people themselves should combine work and rest, pay attention to nutrition, exercise appropriately, and enhance physical fitness to prevent the possibility of low-level hepatitis B virus from becoming active again and evolving into typical Hepatitis B.