Okay so Iove making my dismay lives hard and vector is great for that. I've always been confused after I send them to the hospital I get the pop up box but it says no under identified. So I've always selected one and then it says yes.
my question is are the viruses/diseases that shows up after visiting the Virologist what my sim has and I'm suppose to select one or all or have I been doing this wrong?

Yes, the list is what your Sim is infected with. Selecting them just tells you about them so it doesn't matter how many you select.