SIR

SIR (susceptible infected removed) is an RTS game where the player controls the infection that spreads among humans

In this game you control an army of infected creatures and your goal is to spread the infection.

 You control units like an RTS, units have different abilities and units can be mutated, some can even act as vehicles transporting other units you must attack humans to convert them 

At first humans will not fight but as you spread the humans will try bringing in more and better weapons to stop you

Good luck