Nice graphics, nice sound, fun game-play, and a bit of innovation. I like it. The game draws heavily from the likes of "Infect. Evolve. Repeat." but trades evolution for a kind of virus herding mechanic. The viruses move toward the mouse when it's nearby, so you don't have to drag-and-drop like in I.E.R. While I do like that the game doesn't keep all of the same mechanics, I do think that a kind of evolution or power-progression system would do a lot to keep the game fun while progressing for more than just 4 levels.
All of the layers of moving background do a great job at making the game look like it takes place in the bloodstream. While the background might change for each level, however, not much else does. Having a variety of enemy cells and bodily defense mechanisms, coupled with a kind of evolution system would help liven things up. You can improve the herding mechanic and introduce extra tactics by having a way of repelling viruses instead of attracting them. Clicking for a quick speed boost when you need it most would also reward skillful play.
In short, I like the new moving mechanic, but don't think the game is anywhere near its potential.