I think it is in the Bible. "Sin came into the world through one MAN..." Don't you find this statement a little odd since Eve took the first bite? Wouldn't you think that Paul should have said, "Sin came into the world through one WOMAN..."? Paul had it right because sin is transmitted through the man.
(BTW, Catholics and Orthodox believe nothing remotely like it. Original sin is the inherited lack of grace, not some polluted "Adamic nature" that is transmitted from men.)
You might include some Protestants as well. Reformers are just about the only ones (there are a few others) who believe in original sin.
Quite frankly I don't understand why you think a virgin birth was necessary.
That doesn't say that some sort of "Adamic sin nature" is passed down through the male line. It says that sin came into the world through Adam. That's not the same thing.
Why Adam, and not Eve? It's mysterious, and too long to get into here. Scott Hahn deals with it pretty extensively in his Salvation history tape series, though.
Reformers are just about the only ones (there are a few others) who believe in original sin.
Catholics very definitely believe in original sin. We just don't believe it's what you say it is.
Quite frankly I don't understand why you think a virgin birth was necessary.
Why do you think creation imposes any "necessity" on a sovereign God? No, the Virgin Birth wasn't necessary. In fact, the Incarnation wasn't necessary, either. Nor was Creation itself.