Zombie infection is by far the biggest cause of death in the game and is a hindrance for fun gameplay in its current state. Here's why:
Anticlimactic
Your game ends before it ends. Got in a little scuffle with a zombie and got infected? You're hopeless, might as well kill yourself.
Imbalance
The first aid skill and any occupations focused on it are useless because there's nothing it can do against zombie infection.
Slow Healer is a no-brainer free trait. Fast Healer, First Aider and Former Scout are a waste of points.
The problem with simply disabling infection from your game is that it removes the threat from zombies. Turning on sprinters is also hardly ideal because they make the game a constant campfest where you waltz around fences. This is why I want to suggest a new gamemode to get around this, and put sprinters to good use:
Bloodthirst
A gamemode with no zombie infection. But how are you punished for messing up if there's no infection? Zombies can smell your blood, they will turn into sprinters and your location will be disclosed to them in a radius around you when you are wounded. The size of the radius of attraction depends on the severity of your wounds, whether they are bandaged with clean bandages and the quality of said bandages. Bleeding bites and gashes will attract sprinters in a large area around you, while small bleeding scratches will attract sprinters in a small area. A small fence wound bandaged with a proper clean bandage should not attract sprinters at all.
Why is this good for gameplay?
Climactic
Dying in a bloody battle with zombies is far more exciting than dying to a slow acting disease or killing yourself over said disease. You can still use your skill and resourcefulness to save yourself and have more fun doing it. You can fight until your last breath, and until you are chomped down, there is still hope.
Balance
The first aid skill is now important, and so are its associated occupations. If you can heal faster to shorten the zombie onslaught, that will greatly increase your chances.
Slow Healer now has an appropriate downside that doesn't make it free points. Fast Healer, First Aider and Former Scout are now appropriately useful.
Medical treatment is now more balanced, you actually have a good motivation to change your dirty bandages, use proper bandages instead of rags, and disinfect wounds. Dirty bandages do not reduce the radius of attraction, using proper bandages reduces the radius more than strips of cloth, and wound infection is going to leave you exposed to danger for longer.
Some more clarifications:
-When zombies no longer smell blood, they should go back to normal.
-Zombies are not attracted to rotten zombie blood, only fresh living blood, so being covered in their blood is fine.