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Disease plays a large role in Base icon CK2.png Crusader Kings II, due to the lethality of ailments in the Middle Ages, and generally bad side effects they give to the player character. Most characters are capable of living through the majority of diseases, though some may still die when an outbreak occurs.

All diseases are represented by health traits.


Normal diseasesEdit

Disease Description
  Generic Illness

The most simple type of "disease," the trait ill reduces martial by 1, health by 2, and fertility by 10%.
Unless the ill person in question is very old, weak, or has another disease, the odds of someone dying from this trait is very low.
Generic illness and pneumonia are mutually exclusive. It is needed to have a health level of at least 3 to recover from this disease.
If   The Reaper's Due Expansion is active, the illness trait is replaced by symptoms which will be treated by a court physician.


Incompatible with ill, the pneumonic trait is far far more deadly. It reduces all attributes by 2 and reduces health by 4.
It also reduces fertility by 50%, making most characters very unlikely to procreate. The trait is often deadly; do not expect to have player character rulers survive this one every time.
It is needed to have a health level of at least 4 to recover from this disease.


Another moderate disease, leprosy makes holding a large kingdom or empire together very difficult.
It reduces diplomacy and health by 2, and fertility by 20%. It also reduces sex appeal by 50, and all vassals opinions of their liege by 20.
Though leprosy has a +10 bonus with other lepers, chances are that a character will not make use of that bonus often.
It is needed to have a health level of at least 4 to recover from this disease.

  Great Pox

A moderately dangerous disease, syphilis reduces all attributes by 1, health by 2, and fertility by 20%. Furthermore, it reduces sex appeal of the character by 30.
This disease will most likely shorten the lifespan of the player character, though it will not necessarily result in an abnormally early death.
One of the most dangerous features of this disease is that it can be passed down to children if one of their parents has this trait. This makes long-lived heirs more rare if the ruler suffers from great pox.
It is needed to have a health level of at least 6 to recover from this disease. There is a chance to remove this disease by choosing the Theology focus.

Epidemic diseasesEdit

Epidemics begin with an outbreak in one province, and can spread through adjacent provinces on the first day of each month.

When a county is affected by an epidemic:

  • A dark green cloud appears over the city sprawl
  • Characters living in that province will randomly become infected. Characters who have already contracted and recovered from the disease are immune, with the exception of the great pox
  • City tax income is reduced
  • Supply limit is reduced, and attrition is greatly increased for troops in excess of the supply limit. These effects make warfare harder, especially when large armies are required or multiple diseases are present.

Rulers can protect themselves against epidemics by relocating their capital or by sending individual characters to other locations. Children aged 6-15 can be sent for education to other courts. Adults can lead troops or perform council missions in safer provinces. With   The Reaper's Due, it is worth noting that only land provinces are safe: leading troops at sea while an epidemic ravages your capital is a sure way to contract Scurvy  ; going into seclusion can be considered a viable alternative.

Conversely, sending a character to an infected location can serve as a quiet way to dispose of a rival or an unwanted heir.

Outbreaks always begin in coastal cities. Cities with higher income are at higher risk. A capital which is far inland may be safer. The Black Death historically arrives around 1300-1400 AD, though the player can change it on the game rules panel at the beginning of a campaign.

I suggest not having your capital on a coastal trade post province since disease seems to have a higher chance of spawning there. More importantly it appears that your Hospital level is NOT checked when the disease appears as would normally occur if it's not in a disease spawn site.

It also seems diseases spread through trade ports in the same network.

List of epidemic diseasesEdit

Epidemic Contagiousness Outbreak Duration Trait Effects Recovery MTTH
(for 45yo with 5 base health)
(AKA Tuberculosis)
30% 1.2% 30 months   -2 health 24 months
  Slow Fever
(Typhoid Fever)
30% 1.2% 30 months   -3 health, -10% fertility 4 months
  Camp Fever
50% 4% 10 months   -4 health, -20% fertility 12 months
  The Plague
(Bubonic Plague, Black Death)
95% 1% 10 months   -7 health 3 months
  Measles 60% 3% 8 months   -2 health 5 months
  Smallpox 50% 8% 8 months   -3 health, -25% fertility 5 months
  Great Pox
50% 8%
(  Sunset Invasion)
8 months   -2 health, -20% fertility Recovery ONLY with Possessed   trait

With Reaper's Due expansionEdit

With   The Reaper's Due active, the disease system becomes more complex. Characters will first contract symptoms which will then be diagnosed by their court physician. Hospitals can be built to fight epidemics at the province level and the epidemics also affect the level of prosperity in a county.

An infection   can develop after being Wounded   or Severely Injured  . They can be dangerous as a court physician cannot treat this symptom; the player character may have to make up for the lost health by other means. However, it will heal on its own given enough time, just like other diseases. Counter-intuitively, an infection arising from being Severely Injured   is less dangerous than the same trait arising from Wounded  ; this is because the infection actually replaced Severely Injured   (with no net health decrease), but is added on top of being Wounded  .


Outbreaks can begin in any province, and may spread through single ocean tiles. Infected provinces tend to lose prosperity and may experience its opposite: depopulation. Basic hospitals provide minor protection from depopulation.

Upgraded hospitals can also prevent the county from becoming infected. This makes them useful not only in your capital but also in provinces near your capital, especially at chokepoints such as the Grisons-Lombardy mountain pass.

Certain events may reduce a province's disease resistance: a smugglers' ring forming and refusal to pay for a hospital's upkeep. High prosperity also lowers disease resistance.

The Black Death is larger and more deadly, and gets a chance of major outbreak to occur 200 years into any game, regardless of start date. (This can be changed on the game rules panel.) After a major outbreak has happened, the disease becomes endemic and may break out again, but likely on a smaller scale. The Black Death has special patterns. It may miss India, Africa, Scandinavia, Britain, or the Steppes. It also has a chance to miss a discontinuous region called the Historical Plague Exclusion Zone. Once you see evidence of which regions it is skipping, try to move your capital there.

Epidemics can never spread to Iceland, because it does not share any sea zones. However, Iceland is a small duchy in a weak de jure empire, so moving your capital there may reduce both demesne levies and vassal levies. Iceland is also far from everything else, increasing the risk of independence factions.


Rulers receive the option to go into seclusion when an epidemic spreads to counties near their capital. Alternatively, rulers with the Paranoid   trait can go into seclusion at any time. Rulers must be landed or patricians to shut the gates.

Once the option to go into seclusion is taken, the ruler is isolated together with their courtiers. All secluded characters receive a -5 penalty to their Diplomacy attribute, and can no longer lead armies (if previously able to) or perform jobs (if they are councilors).

If the period of seclusion is too long, negative events may occur, and may result in characters obtaining the Cannibal   trait, becoming Craven   and experiencing food shortages. The ruler can also kick out any courtier who displays any symptoms of disease. Seclusion may fail if a courtier is exposed to the outside world or contracts a disease before becoming secluded.

Upon opening the gates, the ruler gets the Abandoned the commoners modifier. While this modifier is active (1 year), they have -10 general opinion and cannot shut the gates again.


Name Command ID           Health Opinions Other modifiers Possible diseases/Other remarks
  Abdominal Pain abdominal_pain 215 -1 -10% Fertility          
  Chest Pain chest_pain 211 -2 -10 Personal Combat Skill      
  Cough cough 207 -1 -0.25 -5 Attraction          
  Cramps cramps 212 -2 -0.5 -10 Personal Combat Skill    
  Diarrhea diarrhea 209 -2 -2 -1 -5 Attraction -20% Fertility
-1 Personal Combat Skill
  Fatigue fatigue 216 -1 -1 -0.25 -20 Rationality            
  Fever fever 208 -1 -1 -10% Fertility
-10 Personal Combat Skill
-10 Rationality
  Headache headache 214 -1 -1 -1 -0.5 -10 Personal Combat Skill
-10 Rationality
  Infection infection 218 -3 -3 -3 -3 -3 -2 -10 Attraction -10 Personal Combat Skill None
Can appear while Wounded   or Severely Injured  ;adds to Wounded   but replaces Severely Injured  
  Malaise malaise 217 -0.75              
  Rash rash 213 -0.5 -5 Attraction -10% Fertility          
  Vomiting vomiting 210 -2 -2 -1 -5 Attraction -30% Fertility
-10 Personal Combat Skill


Name Command ID           Health Opinions Other modifiers Miscellaneous Cost
  Aztec Disease has_aztec_disease 132 -3 -2 -2 -3 -2 -4 -10 Attraction
-5 General
-30 Personal Combat Skill
-20% Fertility
-3 Personal Combat Skill
  Epidemic (after   Aztec arrival)
  Camp Fever has_typhus 36 -1 -2 -1 -2 -4 -20% Fertility
-40 Personal Combat Skill
  Cancer cancer 230 -3 -20% Fertility More likely when old aged
  Consumption has_tuberculosis 34 -2 -1 -2 -2 -25 Personal Combat Skill   Epidemic
  Dancing Plague dancing_plague 235 -1 -1 -1 -1 -1 -2 -25% Fertility   Epidemic (rare)
  Dysentery dysentery 226 -1 -1 -4 -15 Attraction -25% Fertility
-20 Personal Combat Skill
  Flu flu 225 -1 -1 -1 -1 -1 -2 -10 Attraction -10 Personal Combat Skill Common and brief
  Food Poisoning food_poisoning 228 -2 -2 -2 -2 -2 -3 -15 Attraction -50% Fertility
-10 Personal Combat Skill
  Gout gout 227 -2 -1 -2 -20 Personal Combat Skill
  Has Great Pox syphilitic 27 -1 -1 -1 -1 -1 -2 -10 Attraction
-5 General
-20% Fertility 10% Inherit Chance -44
  Has Slow Fever has_typhoid_fever 35 -2 -1 -1 -3 -10% Fertility
-40 Personal Combat Skill
  Ill ill 25 -1 -1 -10% Fertility
-10 Personal Combat Skill
With   The Reaper's Due DLC, the Ill   trait is replaced by symptoms
  Leper leper 28 -1.5 -15 Attraction
-20 General
-95% Fertility
-25 Personal Combat Skill
  Measles has_measles 38 -2 -1 -2 -10% Fertility
-30 Personal Combat Skill
  Pneumonic pneumonic 26 -2 -2 -2 -2 -2 -4 -50% Fertility
-35 Personal Combat Skill
  Rabies rabies 229 -3 -2 -3 -2 -7 -20 Attraction
-5 Vassal
+30 Personal Combat Skill
-50 Rationality
  Scurvy scurvy 238 -1 -1 -1 -1 -1 -3 -20 Personal Combat Skill Gained when leading troops at sea.
More likely after 3 years at sea.
More likely when an epidemic is ravaging your capital
  Sickly sickly 144 -2.5 Children can be born sickly.
Removed between the ages of 2 to 6
  Smallpox has_small_pox 39 -2 -1 -2 -3 -25% Fertility
-100 Personal Combat Skill
  The Plague has_bubonic_plague 37 -2 -3 -2 -3 -2 -7 -50% Fertility
-100 Personal Combat Skill
  Epidemic (nearly mapwide, many special events)

See alsoEdit