All my citizens are getting sick how do I stop it?

[Dwane Dibbly]

I'm geniunely confused as to why this is happening.

[Blake Walsh]

If you click on a building with a problem, you can mouse-over the problem icon and it will give you an explanation. Most likely you are forcing cims to drink poo water - make sure there is no water tower in a polluted zone, or (less likely) a pump sucking up polluted water.

[shoudo]

Give em fresh water,fresh air and try to lower noise pollution.

[Dammit_Jeff]

Might be the water is contaminated. Check that your water pumps are as far apart as possible from the Sewage pumps.

Either that or add a few clinics or hospitals nearby, that might help.

[Frogshackle]

Sounds like a water tower built on land that is being polluted by industry.

[Trogdor]

If you are using water pumps in a river check the direction of flow. If the sewage outlet is upstream from the intake then you will basicaly poison your city. Also fun to remember if you ever get tired of thier complaints.

[Justin]

Also check your hospitals and ensure they're:

-Not overcrowded
-Their ambulances are not stuck in traffic
-Covering the city

[Justin]

Noise pollution also causes sickness, check your noise pollution infoview and make sure it doesn't overlap. Adding decorations (grass, trees) or sound barriers for your highways will reduce noise pollution

[grapplehoeker]

I hate sickness. Not only does it limit growth, but also results in the necessity for health services which cost too much and creates unwanted increases in traffic from ambulances. For this reason I try to build sickness free cities. I rarely build any clinics or hospitals, except perhaps for the Medical Centre monument in the mid to late game, just because it's so efficient.
The way to avoid any sickness is simple. You just need to be aware of what causes it.
Only residential zones are affected. Therefore do not zone them within the radius of any ground polluting or noise polluting structures/zones. Do not zone residential next to industrial obviously and certainly not next to commercial either.
Do not zone residential near heavily used roads as heavy traffic also creates enough noise to cause sickness. Plan ahead accordingly, you should know which roads you intend to upgrade as your city grows and therefore which will see increases in traffic. Use your overlays!
The only cause of fatal sickness is water pollution. Your water pollution overlay should always show 0%. Even 1% is enough to cause citywide sickness and fatalities. Always, therefore be aware of the placement of your water sources.

[Blake Walsh]

I also build largely sickness free cities (or at least sickness-minimal). I have built entirely sickness free cities but prefer to tolerate a little bit of sickness.

One thing worth noting about the Medical Clinic is that out of all the Police, Fire and Healthcare buildings it provides the best service rating per $. This makes it good for providing a "generic" service rating boost if all you need is the rating and not actual service vehicles. Ironically because the ambulance dispatch is so stupid the medical clinic is only really useful in a sickness-free city.