The four infectious diseases are hepatitis B surface antigen, hepatitis C antibody, syphilis spirochete antibody and HIV antibody, which are a basic screening test for hepatitis B, hepatitis C, syphilis and HIV. If it is a patient, further treatment is needed. Positive hepatitis C antibody requires further investigation of hepatitis C virus RNA, which is also positive, and should be further treated with antiviral therapy. Those who are positive for syphilis spirochete antibodies need further confirmatory tests, and those who also have meaningful confirmatory tests should be treated with early anti-syphilis treatment. Those who are positive for HIV antibodies need to have a confirmation test for HIV antibodies. If the confirmation test is also positive, they can be identified as AIDS patients or HIV carriers and need to start antiviral treatment as early as possible.