How do STDs work exactly?

Question

So we are always taught that STDs come from sexual contact with a person that has been infected.

But how does the infected person get infected in the first place?

There has to be a primary way where someone get infected (not through sex) and then transmits that to others through sex right?

I would imagine that bec we do have treatments for STDs they would go extinct if the only way of getting and STD was through sex. But that isn’t the case.

In: Biology

Answer 1

If someone gives birth naturally with an STD they are able to pass it onto their child if their STD is in its contagious stage.