疾病可由事件触发，并可对小国家造成致命的影响。
In general, diseases will happen if the population does not have its needs fulfilled. Especially the needs of the poor population is important. Therefore, poor countries are more suspectible to diseases. If the player taxes the population too heavily, it increases the risk of diseases.
Diseases are in general more severe to small countries, as many of the diseases will hit a random state or province and kill a certain percentage of the population. If the country have few or only a single state, the risk of hitting important population centers is higher.
Diseases will kill POPs, and usually also have a list of other smaller effects, both positive or negative.
Several techs in the chemistry and electricity column will have an effect on diseases including Organic Chemistry, Inorganic Chemistry, medicine and electricity. Other inventions and research will not have an effect on any disease. Neither will the public health care reform
Different kinds of diseases
Tuberculosis
It can be triggered if the poor strata (
craftsmen, 
farmers, 
labourers, 
soldiers, and 
slaves) does not have at least 80% of their everyday needs fulfilled.
It has a mean time to happen of 800 months (66 years). That is reduced by 10% if the poor strata does not have 90% of their life needs fulfilled and further 10% if the poor strata does not have 70% of their life needs fulfilled.
It can be halted by researching Organic Chemistry, which increases the mean time to happen by 50%.
Tuberculossis will kill 4% of all POPs in a random state, but reduce militancy by 0.5 in that state.
Famine
Famine can be triggered if the poor strata does not have at least 80% of their everyday needs fulfilled and if the government form is not a democracy.
It has a mean time to happen of 800 months (66 years). That is reduced by 10% if the government form is proletarian dictatorship, but increased by 50% if the government form is HM's Government.
It can be halted by researching Organic Chemistry, which increases the mean time to happen by 50%.
Famine gives the player two choices.
- To mitigate the famine at the expense of 5% of the nations yearly income + 1500£. 4% of poor POPs in a random state will still die in spite of the effort.
- Or to do nothing, which kills off 10% of the poor POPs in said random state.
Typhoid Fever
It can be triggered if the poor strata does not have at least 90% of their everyday needs fulfilled.
It has a mean time to happen of 800 months (66 years). That is reduced by 10% if the poor strata does not have 80% of their everyday needs fulfilled and further 10% if the poor strata does not have 90% of their life needs fulfilled.
It can be halted by researching Organic Chemistry, which increases the mean time to happen by 50%. Additionally if the average consciousness is above 4.0, the mean time to happen is increased by further 50%. Over time, the disease will be less severe. The mean time to happen is increased by 1.1 4 times; after 1850, 1970, 1890 and again after 1910.
When the event happens, the player has two choices. In option 1, typhoid fever will kill 10% of all POPs in a random state, and in option 2 only 4% will die, but militancy will increase by 2.
Smallpox
Smallpox can be triggered if the poor strata does not have at least 50% of their everyday needs fulfilled.
It has a mean time to happen of 800 months (66 years). That is reduced by 10% if the poor strata does not have 90% of their life needs fulfilled and further 10% if the entire population does not have 90% of their luxury needs fulfilled.
It can be halted by researching Organic Chemistry, which increases the mean time to happen by 50%.
Again, the player has two choices. In option 1, it will kill 15% of all POPs in a random state and decrease militancy by 1. In option 2 only 10% will die, but consciousness will increase by 2.
西班牙大流感
1918年流感大流行，更广泛的被称为西班牙大流感（西班牙大流感的中文维基页面）, can be triggered if the poor strata does not have at least 90% of their life needs fulfilled.
It has a mean time to happen of 3000 months (250 years/roughly every 3rd playthrough). The mean time to happen is reduced by 10% if the poor strata does not have 90% of their everyday needs fulfilled and further 10% if the poor strata does not have 90% of their life needs fulfilled. The mean time to happen is increased by 50%, when Organic Chemistry is researched.
Unlike the previously mentioned diseases, the Spanish flu can spread from country to country. If any bordering nation has had this event, the mean time to happen is decreased to a mere 1% (30 months).
You have 2 options:
- Fight the disease with every available mean which costs 5% of the nations yearly income, but in return the disease will only last for 12 months.
- Not really, why? which does not cost anything but the disease will last for 18 months.
While the disease is ongoing 0.1% of the population of the entire country will die every month and consciousness will increase by 0.1 pr. month.
The disease is called 'Strange Influenza' in the event game files.
Cholera
Cholera can happen in a country if the poor citizens do not have at least 95% of their everyday needs fulfilled. It has a mean time to happen of 250 months (roughly 20 years). It is decreased by 25 months if the poor strata does not have 90% of their life needs fulfilled, another 25 months if they do not have 85% of their life needs fulfilled and yet another 25 months if they do not have 90% of their everyday needs fulfilled.
On the other hand, the mean time to happen is tripled to 750 monts (roughly 60 years) once medicine has been researched, and again doubled to 1500 months (roughly 120 years) once electricity has been researched.
The amount of provinces also have a say in the meantime to happen. If the country has more than 10 cities, It is increased by 50% for every 5 provinces owned up to 40 provinces.
For this disease the player has two choices:
- Quarantine the province which decreases pop growth in a random province by 1% for 180 days. On top of that it inceases consciousness by 2 and lowers militancy by 1
- How bad can it get? which decreases pop growth by 2% for an entire year. On the other hand, consciousness is reduced by 2. Furthermore it risks spreading to other provinces.
In the game files it is not listed in the file 'diseases' like the others, but for unknown reasons in liberalrevolutions.txt
The spread of Cholera
The disease can spread to neighbouring province, if the poor strata still doesn't have 95% of their everyday needs fulfilled, and if the player have not quarantined the province.
The event, that spreads the disease has a mean time to happen of 100 months (roughly 8 years), which is reduced by 10 months if the poor strata does not have 90% of their life needs fulfilled and further 10 months if they do not have 90% of their everyday needs fulfilled. The mean time to happen is increased by 300% if medicine has been researched and further doubled if electricity has been researched.
Once again the player has the choice between quarantining the province or not:
- Quarantine the province which decreases pop growth in a random province by 1% for 180 days. On top of that it inceases consciousness by 2 and lowers militancy by 1
- How bad can it get? which decreases pop growth by 2% for an entire year. On the other hand, consciousness is reduced by 2. Again it risks spreading to yet other provinces.
Potato Blight
A potato blight can happen to any civilized country in Europe, which has not invented Inorganic Chemistry. The event will be called 'The Potato blight of [current year].
It has a mean time to happen of 250 months. That is reduced by 25 months if the country has not researched medicine. It is reduced by 50 months if the poor strata does not have 80% of their life needs fulfilled, but increased by 125 months, if they have 95% of their life needs fulfilled.
The event will have effect on a random owned non-colonial state and will decrease pop growth by 2% as well as increase militancy by 0.01 pr. month.
The player has two choices
- Spare no effort in relieving the local farmers which will have the effect last 6 months, but on the other hand the local population will gain 3 consciousness and the country will lose 2 prestige.
- Let them eat cake which will have the disease last 12 months, but will not have an effect on consciousness and prestige.
Like the Spanish Flu the event is not placed in the disease file but in the LiberalRevolutions file