I've lost track of all the sub-threads here, so hopefully nobody's already said this:

I'm starting to agree with the folks getting creeped out by Tanya. I didn't think much of it while listening, because I know what it's like to get a rush out of experimental progress in science. Now I'm wondering if perhaps she knows more about Z-day that she's said.

What we know:

1. She's a vet.
2. She's been bitten.
3. She's either turning slowly or not at all.
4. She gave drugs to Saul that were supposedly potent antibiotics.
5. She has iffy bedside manner.
6. She's getting a rush from her autopsies and experiments.

What if she worked for Raydon, or some associated or subsidiary company? What if she was doing animal experiments that somehow precipitated Z-day? What if she didn't just give antibiotics to Saul? What if she has some idea of how to stop or reverse the transformation/mutation effects of the "zombifying" vector (be it gas, virus, bacteria, whatever) because she helped develop (or at least test) it?

Did Tanya work for Weyland-Yutani Corporation?