Use condom in each sex can prevent HIV and STDS. HIV can be spread during vaginal sex when HIV-infected semen, vaginal fluid or menstrual blood comes into contact with the mucous membranes of the vagina or penis. Some STDs (gonorrhea, chlamydia, trichomoniasis) are spread the same way as HIV. Other STDs (herpes, syphilis, chancroid) are transmitted through contact with infected …