This app was mentioned in 4 comments, with an average of 1.50 upvotes
I was going to suggest Please Stay Calm, but when I was double checking the title I saw Zombie Outbreak Simulator which sounds closer to what you described.
Was it about simulating a zombie outbreak on a GPS map? There was a flash version on onemorelevel.com back in the day, but I know there's an android version just called "Zombie Outbreak Simulator." Uses a lot of the same sounds and graphics, so I'm pretty sure it's the same thing.
https://play.google.com/store/apps/details?id=com.binaryspacegames.zombieoutbreaksimulator
Is it Zombie Outbreak Simulator?
https://play.google.com/store/apps/details?id=com.binaryspacegames.zombieoutbreaksimulator