as far as I know, the nordwave doesn't come with a neat VST plugin like the virus does

so to hear it, you would have to go through the virus' audio input since it's your only audio device.
what bothers me is that when you play the nordwave's keys using it as a MIDI keyboard to play the virus, you'll probably have to mute the nord's audio out (or deactivate the according audio channel inside ableton) because you'd end up hearing both synths. yeah, I know, it's not a big deal to push a button - I just think it would be quite a pain in the ass to keep thinking about that during hours of work, it disturbs the flow (that's why I use rack synths if possible and control them all with 1 keyboard). but that's just me.
off the top of my head, I am not able to say if it's possible to do an "audio through" routing with the virus inside ableton using the routing options alone or if it will be necessary to use an input patch on one free bank of the synth. in any case, I'm pretty sure there will be slight delay issues, but first things first. I will try this in the evening when I get home (I don't have a nordwave, but pretty much any other hardware synth will do) - stay tuned.