At each visit, blood sample will be collected to test for HIV, hepatitis B and C, and syphilis. at the Faculty of Associated Medical Sciences. Laboratory examinations will be free of charge for all participants. After the blood draw, participants will be invited to complete a questionnaire to assess their knowledge, attitudes and practices with regard to HIV and other infections. Test results will then be provided. In case of confirmed HIV infection, participants will be provided with further counseling, CD4 cell count measurement and referral options for immediate treatment. Blood samples collected during the study for the diagnosis will be stored for determination of the Fiebig stage (duration since HIV primary infection), evaluation of transmitted HIV drug resistance (sequencing) and investigation of viral transmission networks.