It is also worth mentioning that the herpes virus doesn't necessarily spread through exchange of sexual fluids or sexual contact. (herpesdating-sites.com)
Trichomoniasis is spread through contact with sexual fluids like semen (cum), pre-cum, and vaginal fluids. (plannedparenthood.org)
And with HIV, condoms are a highly effective mode of blocking disease transmission because the virus is primarily spread via contact with sexual fluids or blood. (scientificamerican.com)