Surface antigen usually refers to the hepatitis B virus surface antigen (HBsAg) and if positive indicates a hepatitis B virus infection. Hepatitis B surface antigen is the antigenic component of the hepatitis B virus envelope, which can generally appear in the blood as early as 1 week and as late as 12 weeks after infection with the hepatitis B virus. Hepatitis B virus infection can be clinically manifested in the following forms: 1. Acute hepatitis B: Patients have obvious symptoms of hepatitis, such as fever, malaise, nausea, aversion to grease, loss of appetite, with or without yellow urine. About 90% of perinatal infections turn into chronic hepatitis B, 25%-30% of infant infections turn into chronic hepatitis B, 5%-10% of adolescent and adult infections turn into chronic hepatitis B. 2. Chronic hepatitis B: Hepatitis B surface antigen remains positive for more than 6 months as chronic hepatitis B. Most are asymptomatic or have mild hepatitis symptoms. If HBV-DNA (hepatitis B virus deoxyribonucleic acid) is positive, it meets the indications for anti-hepatitis B virus and generally requires anti-hepatitis B virus treatment. If untreated, it can progress to cirrhosis and liver cancer; 3. Hepatitis B virus carrier: no liver damage and no clinical symptoms. It can be manifested as HBV-DNA positive or HBV-DNA negative. The former is infectious and the latter is basically non-infectious. Virus carriers also have conditions that require antiviral treatment, and the need for treatment should be judged by a professional doctor. If you are positive for hepatitis B virus surface antigen, you need to further check the five hepatitis B items, HBV-DNA, liver biochemistry, abdominal ultrasound, liver elasticity, and your doctor needs to give a specific diagnosis and give the corresponding treatment measures by combining the patient’s clinical manifestations and related tests.