Hiro asks the Librarian what the tree thing is, and learns that it's a totem of the goddess Asherah. Apparently there are versions of this goddess in a lot of different mythologies. Her name translates into Eve and she has snakey connotations.
A lot of ancient peoples worshiped Asherah, until a bunch of Jews decided to get rid of her. They reformed their laws through Deuteronomy, which served as an inoculation against the Asherah virus.
In this sense, any religion is like a virus, using the human brain as a host.
The Librarian compares the Asherah virus to herpes simplex, which is a virus that moves into the nervous system and just never leaves; the two may even be related.
Further, Asherah worship involved cult prostitutes, so there'd be bodily fluids spreading the virus too. Mmm, virus-lovin'.
There's more talk of how this all relates to Adam and Eve (Eve was like another version of Asherah, but the story itself might've been a political allegory invented to warn off enemies). Even better, there's biblical evidence that a king of Jerusalem figured out how to poison the army of Sennacherib, the king of Assyria, before he could assault Jerusalem. Viruses and poisons, sounds like fun.