Fallout 4 diseases

Diseases are an integral part of Survival mode in Fallout 4.

Overview
There is a chance of contracting a disease after eating uncooked meat, drinking unpurified water, taking damage from disease-ridden creatures, and using harmful chems; diseases convey a general drawback after contraction. Items that cleanse the body of radiation also come with the side effect of a suppressed immune system, leaving one more vulnerable to contracting a disease. Only one disease (mole rat disease) can be obtained outside of Survival difficulty; otherwise, the other six diseases require Survival difficulty being active to contract.

Diseases can be cured by visiting a doctor and paying them to remove it. Alternatively, antibiotics can be used to get rid of diseases. Furthermore, prophylactic herbal remedies can be crafted at chemistry stations to lessen the chances of contracting certain diseases in the first place.

Contracting

 * The chance for contracting a disease is determined by a roll, depending on the current Disease Risk Pool (DRP). The DRP is a cumulative indicator of the current risk of the character becoming diseased and starts at 0, accumulating percentage points from various environmental and food/drink sources. The DRP decays at a natural rate of -1% per game hour.
 * Sources include:
 * Food always adds +1% to the DRP (but does not force a roll). Foods can also have a low disease risk (+3% to the DRP), standard (+7%), high (+12%), or very high (+20%).
 * Drinking Nuka-Cola adds +2% to the DRP (does not force a roll).
 * Chems add +7% to the DRP. These include Buffout, Calmex, Daddy-O, Day Tripper, Fury, Jet, Med-X, Mentats, Overdrive, Psycho, and X-Cell.
 * Fighting infected enemies will add +5% to the DRP if hit in combat.
 * Swimming in contaminated water will add +3% to the DRP. The effect stacks every 2.4 game hours (10% of the game day).
 * Exposure to rain adds +3% to the DRP every 12 hours.
 * When the DRP reaches the threshold of 25%, it starts rolling for diseases.
 * All items that cause immunodeficiency to add 20% to the global chance to contract the disease for the duration of the effect and add a separate +5% to the DRP.
 * If the game rolls a disease, it is added as an effect and the player character receives a grace period: They cannot contract another disease for the next 24 hours.

Diseases

 * When the game rolls for disease, the disease die roll needs to be lower or equal to the current DRP. All diseases have a 5-90% chance of occurring (i.e., the game will randomly select among them to apply it).
 * If the player character has taken the appropriate herbal remedy, the value must also be higher than the BoostedImmunityThreshold to get this disease. This number acts as both a minimum Risk Pool threshold to even get this disease and once the Risk Pool is high enough, add some randomness to whether the player character gets this disease with each risky action.
 * Every disease has a chance floor and ceiling to be contracted, which will always drain to the floor value.