HIV can be detected at 3 weeks, if HIV antibody test is used, HIV antibody can be detected in the patient’s blood after 3-4 weeks of HIV infection, HIV antigen antibody can be detected in the blood after 2-3 weeks of infection, HIV-RNA can be detected in the body of the infected person after 7-10 days of infection, therefore, if the infection is 3 weeks of HIV infection, the patient’s HIV-RNA and P24 antigen can be detected. Therefore, if the patient is infected with HIV for 3 weeks, the diagnosis can be made by examining the patient’s HIV-RNA and P24 antigen. If the patient is found to be infected at this time, the patient should be treated with antiviral drugs as soon as possible to prolong the patient’s life and to give him/her a good prognosis, because the start of antiviral treatment is very early, only 3 weeks after infection, and the prognosis is significantly better than that of other AIDS patients.