I love games that relate to viral science and not necessarily zombies.
This game is incredible but surely, you can add more levels by adding rules/stipulations/challenges to each levels. New and interesting bonuses. New and interesting "enemies". Make more research on the viral world and impact the player with your new found knowledge on how to make infecting a host a more challenging task. Just don't kill the controls like other developers have, will ya? Mouse or arrows sounds good to me (preferably arrows, I accidentally scroll on my touch pad).