You may come across zombies whom will increase your infection level. once it reaches max, you will instantly perish. To prevent this you can do this in one of two ways. One is much simpler, the other takes a little more work:
Disinfectant Tablets:
You can find these further in on the map, or on nurse zombies. These will decrease a small amount of infection.
Disinfectant Shower:
This requires 3 items: a Medical station, Disinfectant Cabin, and a container of Disinfectant.
1 - Find vials in boxes or on zombie nurses.
2 - Craft a medical workstation, and use the vials, rags, and empty bottles to form one container of Disinfectant.
3 - Craft a Disinfectant Cabin, and shower using the container of disinfectant.
All infection should dissipate after showering. Good luck Survivor!