So, it's like a cross between Left 4 Dead, an RTS, and RPG, and some really annoying music...
http://www.kongregate.com/games/TogeProductions/infectonator-world-dominatorThey released a couple of proof of concept short games which I played to death a while back, but this is something else- it's massively larger and in depth. I'd recommend turning the music off though, unless you like soul destroying synth stuff.