First of all I wanna mention that I am a very big fan of the "virus games" and have played quite a few of them. With that said, I want to congratulate you on a job very well done! The overall feeling was really good, the gameplay was fun and well-made and the music and art were really fantastic! What I liked the most was the last level. The background and music for that stage are truly remarkable! Just to be on the safe-side, they are the "last level treat" right?
Otherwise, you have my 5 stars!