I expanded all my clinics and had them covering my whole city so everything was bright green. I also had a zombie outbreak but the sun came out and they crumbled. The cure seems to be ease of access and upgraded clinics / hospitals.
Your first town will largly feel like a waste of time when it's all said and done. I know that after I got on a roll last night my city layout turned out to be crap and I restarted and things were much more efficent.