Spreading a virus turning humans into zombies, this style has been already used. Flash game Chain Soldier is something similar but it’s more about turning soldiers on your side and so eliminating all guys.
The principle is spread a “virus” among all moving units until no one is alive. The types of soldiers are various and I never knew what is exactly what. So click, collect gold and upgrade. The content is simple but for relaxing after hard work it’s great. The luck is needed as well so it can happen you try one level 10 times.