Plague

Plagues are Natural Disaster.

## At a glance

* Possible from 1350 to 1650, but become progressively weaker
* Kill large numbers, especially urban pop
* Destroys some fluid wealth
* Spread through adjacency and Centers of Trade

## Overview

While the most devastating outbreak of the Black Death swept through Europe shortly before game start, smaller bouts of plague will hit pockets until 1650. The first 2-3 epidemics pose a severe threat and countless thousands will die, but over time they will gradually become smaller and smaller until finally stopping completely.

### How Plague Spreads

Bubonic Plague historically spread west across asian trade routes, onto European trade ships and took hold in certain important ports. In game, plague will first appear in an important coastal Center of Trade and will spread to the surrounding region. When a province is infected, it has a chance to infect all neighboring provinces based a variety of factors. Plague will rip through densely settled provinces easily and with devastating effects on urban and rural populations. It will have difficulty, however, spreading across harsh terrain, areas of low infrastructure or expanses of low population, reducing in strength until eventually petering out. Plague can rebound, however, if it infects another large city, spreading with rekindled strength. Once a province has recovered it cannot become reinfected during that outbreak.

Besides spreading through adjacency, plague infested ships will cause outbreaks semi-randomly in other CoT, with the more prominent centers having the greatest chance. This poses a great risk to highly urbanized and affluent regions that tend to have lots of large CoT and cities. Besides being more likely to pop up in one of these ports, surrounding cities can serve as incubators that increase the plagues strength and chance of spreading further to other provinces. Being highly urbanized is not without risk.

Lastly, infection can spread to ports within a seazone of an infected province. The chance is modified by the port infrastructure present, with larger, busier shipping centers more likely to be severely infected.

### Effects and Recovery

Plague can ravash populations immensely, killing between 50% and 10%. A percentage of fluid wealth is also destroyed based on the plague's intensity, but unlike other trauma it leaves asset wealth unaffected. The chief factors that determine how much time it takes a province to recover are plague intensity and population size relative to ideal population.

The intensity of plague in a province is determined by comparing a province's innate susceptibility times the infecting province's intensity. Urbanization, terrain, policies, events [and other stuff...?] determine innate susceptibility.

The second factor deals with the population growth model. If a population is above its carrying capacity, ie. ideal rural pop or urban gravity respectively, it grows more slowly due to diminishing resources, food, opportunities etc., with the opposite true for a population below its carrying capacity. Therefore, if two identical plagues hit an overcrowded and an undercrowded province, the undercrowded province would bounce back to its pre-plague population in little more than a decade, whereas the overcrowded province may take forty years to rebound fully.

## Examples

In this first image, you can see the beginning of two plague outbreaks in Seville and Valencia. The initial outbreak is worse in Seville, given that it is a larger center of trade and in a more urbanized region.

After 3 months pass, we see the plague spreading outward in all directions. You'll notice the plague is always worse around wherever ground 0 is. Large cities and major centers of trade tend to serve as incubators for the plague. That's why, in western Andalucia, you see so much red. Amenable terrain, numerous roads, and large cities are perpetuating the plague.

Now let's skip ahead again...

Now we see the plague at its fullest extent in Spain. You'll notice that as soon as the plague starts running into more remote areas, rough terrain, mountain passes, etc. it begins to dissipate. As the plague attempts to penetrate Portugal, it slows dramatically due to no road connection and hilly terrain. This is especially true up in norther Spain, though once you hit those nice farmlands of Galicia, you see an uptick in the plague. Up on the border of Spain, you can see a halt to plague entirely as it fails to pass across the Pyrenees.