What are the links of the chain of infection?

Vaginal infection: often caused if you have sexual intercourse with either male or female, when having an orgasm or simply being wet, [with a male] & the male has precumed that cum stays in your vagina. If you have sexual intercourse with different males(3-more), although you may not do them at the same time the previous guy's precum will stay there until you wash your vagina with a dooche water(what's inside of a dooche bag) or wait until your own body expulsion, which is when you have your period. This, my friend causes infection as well as other things, this may also cause HIV.

Penis infection: Males are lucky to have a penis, due to the fact that it is not inside; it is not as easy to create infection, however if you don't wash after having vaginal or anal sex intercourse you may get an infection. If you don't wash & happen to be lucky and have sex with another girl before washing, you may create an infection for her easier than for you. What I recommend is to stay clean.

To avoid having an infection, I recommend using condoms. They will keep you from getting infections, HIV & I'm worst cases getting pregnate without planing to become parents. Wash after having sex & avoid things such as threesomes.