Overview:
Diseased introduces an enhanced disease system to Skyrim. In vanilla Skyrim, diseases consisted of simple debuffs acquired after contact with an animal, and were cured with a relatively small amount of effort. In Diseased, diseases grow and weaken in strength over time, and necessitate greater engagement from the player to treat.

This mod was designed by manaflow to make Skyrim's diseases more immersive, and I have tried to expand upon that as much as I could. But, at the end of the day, this mod might not be for everybody. I have added a lot to the MCM to try and make the mod as customizable as possible, but if you feel unsure, I strongly encourage you to try it out before adding it to your load order. It can really change the way the game plays, -a bit like Frostfall imo-. While I personally loved the original mod, I understand not everyone is looking for the same experience.

1.Progression:



Diseases have 6 stages; the effects a disease's first stage are almost unnoticeable, whilst the effects of its final stage are crippling (perhaps literally). Each disease has been assigned its own “evolution check” time period. When an evolution check occurs, a disease will evolve, recede, or stay the same. Some diseases have longer periods of time between "evolution checks", and therefore take a longer period of time to advance or recede, whilst others might advance to their final stage in a matter of days.

Below is a list of the exact amount of time between evolution checks for each disease. However, this information can also be gathered from in-game sources if you wish to avoid spoilers (which is how I would personally recommend approaching this mod).

Disease effects for vanilla diseases are largely the same as they were in vanilla Skyrim (although comparatively weaker or stronger depending on the stage of the disease), but additional side-effects have been added to make them more interesting. For instance, Ataxia, which causes hand tremors, can cause the player to suffer a hand spasm during combat and other physical activity (which can be disabled in the MCM if not to your liking).

2.Advancing and Receding:
When an "evolution check" occurs, the mod first checks whether a disease meets the conditions necessary to evolve. If not, a second check is made to see if a disease meets the conditions necessary to recede. The probability of progression or recovery is heavily influenced by certain factors:
a)Disease Resistance: Disease Resistance is a value which exists in vanilla Skyrim and is influenced by a variety of in-game factors. For instance, certain races have innate Disease Resistance. Higher Disease Resistance reduces the chance a disease will evolve, and increases the chance it will recede. Lower Disease Resistance Values increase the chance both checks will fail. A 100% Disease Resistance value will yield a 100% chance to pass both checks, forcing the disease to recede by one stage. Factors which impact Disease Resistance include Vampirism and Lycanthropy, which provide 100% Disease Resistance, various magic enchantments and the dragon mask Hevnoraak.
b)Health: The player's Health stat directly increases the likelihood that both evolution checks will be passed.
c)Rest: Having the 'Well Rested' trait or its marriage-equivalent increases the likelihood that both evolution checks will be passed.
d)Location: The player's location impacts disease progression. Unhygienic locations, such as dungeons, cemeteries increase the likelihood that a disease will evolve, whilst sterilized and homely environments such as the player home, temples, inns and other city locations will help improve your condition (albeit, the bonus varies from location to location). Generally speaking, the cleaner the area, the better!
d)The consumption of medicinal mixtures, alchemical potions and gaining the blessings of a god.
e)Disease stage: This is perhaps one of the most significant factors, and part of what can make the mod so challenging. Recovering from a disease in its early stages is significantly easier than recovering once is it has advanced to its later stages. It is important to try and take care of a disease as early as possible, or strong medicines and potions, which can be hard to come by (depending on settings in the MCM) will be needed to be cured.
f)Randomness: There is a small degree of randomness. This will not effect players with 100% Disease Resistance.

3.Treatments, Crafting and Diagnosis

a)Medicines: Every disease has its own distinct remedy that the player can buy and craft. The player can learn to craft several of them after opening the book “Natural Remedies”, which can be bought from most merchants. Herbal remedies can be used to cure more mild illnesses such as coughs and colds, and can be crafted by reading "Minor Illness in the North'. These treatments can only be created in a cook-pot due to engine limitations.
b)Alchemy Potions: In addition to medicines, most diseases are accompanied by a potion. A potion, when taken, ensures that the disease it is designed to treat will decrease by one stage when its next evolution check occurs. The player can create them at alchemy tables using newly added ingredients in the mod. All ingredient spawns can be disabled in the MCM. These ingredients and their effects are:
The normal, non-specific "Cure Disease" potions from vanilla still exist within the game, and can be crafted and bought exactly as they could be in the original game. Unlike other alchemy potions in the mod, they work on all diseases. However, they are now only effective between the time a disease is first caught and its first evolution check; otherwise known as an "un-evolved disease".  As such, they will have to be taken soon after a disease is first caught in order to have any effect. This mechanic is slightly modified from Manaflow's original mod. See the New Features section for more details. 
c)Alchemy Skill and Diagnosis: When players first contract a disease, it will be undiagnosed. Depending on the player's Alchemy level, and the medicinal books they have read, the disease has a chance to be diagnosed, either when it is first contracted, or every time an evolution check occurs (automatic disease diagnosis can be disabled entirely in the MCM, leaving it up to the player to manually diagnose every disease from the symptoms they have).
d)Other forms of Diagnosis: Vigilants of Stendarr will diagnose and treat the player's illness for free. If enabled in the MCM, priests will also diagnose and treat diseases, but will have to be paid (for a price that can be customized in the MCM).
e)Poisons: It is also possible to buy and craft poisons that will apply the effects of a disease to NPCs. These are detailed in the in-game work "Grayfox’s Anatomy”.
f)Blessings: As was the case in vanilla, gaining the blessings of the nine divines or a daedric prince can go a long way. Praying at altars yields a random % Disease Resistance bonus, and can even cure all diseases instantly if a ritual is performed. This ritual is outlined in-game in “Grayfox’ Anatomy”. It involves:

4.Books:

a)Basic Medicines: There are two major books in this mod that detail the disease system. The first and most basic one is “Natural Remedies”, which explains in detail how diseases can be cured. Reading the book will allow the player to craft basic medicines for the diseases present in vanilla Skyrim at any cooking pot using common ingredients.
b)Average Medicines: The second most prominent book is called “Grayfox’s Anatomy” . It covers the symptoms of each disease and the recipes needed to craft slightly better medicines. It provides further information on the impact that alchemy and blessings can have upon contracted diseases. “Natural Remedies” must be read before this book.
c)Advanced Medicines: Finally, every disease has an accompanying compendium or book named after it that further details their symptoms and stages. Reading a compendium will allow the player to craft the strongest medicines present within the mod. "Grayfox’s Anatomy" must be read before these books.
d)Medicines for New Diseases: I have added a significant number of new diseases in my conversion of this mod, all of which are present somewhere within the Elder Scrolls' lore. These diseases are not covered within “Natural Remedies”  or "Grayfox’s Anatomy” directly. Instead, each new disease has its own separate book (like the compendiums for the original diseases) that can be found throughout Skyrim. In order to craft the most basic medicines available for these new diseases, the player will still have to read “Natural Remedies” first. Once they have, reading one of the new diseases' unique books will add the recipe for that disease's accompanying basic medicine at the cookpot. Once "Grayfox’s Anatomy” has also been read, reading these books will allow the player to craft average and strong versions of these medicines.
e)Herbal Remedies: Finally, herbal remedies can be crafted once 'Mild Illness in the North' has been read, which can be used to treat less severe illnesses such as colds, coughs and migraines.

IMPORTANT: Each book lists the ingredients required to craft each medicine. In my version of Diseased, I have added an option in the MCM to enable complex medicine recipes. If this is enabled, each new stage of medicine will require an additional two ingredients in order to create. If you do NOT have complex recipes enabled, you will only need the FIRST ingredient listed for each recipe within the book in order to craft a medicine. If you are still unsure, I recommend checking out recipes as they are listed at the cook pot. Sorry, convoluted...I know... but it doesn't seem to be possible to change what is written in a book from an MCM. :(

Names of books and what they can help cure:

5.Fatal diseases
In the original mod, all diseases, with the exception of Ataxia and Rattles, were fatal, and drained the player's health, magicka and stamina after the disease's final stage. With my additions, there are now several new fatal and non-fatal diseases.

6.Random, "Dynamic" diseases and Mild Illnesses

The player can now catch diseases whilst traversing Skyrim's wilderness. Infection, of course, is more likely in certain locations. Some locations may even be liable to infect the player with a specific disease (Hagraven coves *cough*), whilst presence in other locations will almost never result in an infection. Reasonability is maintained here. It is rare that the player can be infected dynamically, and diseases that necessitate a specific form of contraction, such as Sanguinare Vampiris, can never be contracted this way. Infection rate can also be adjusted in the MCM.

In fact, dynamic infection rates were so rare in the original mod that I've created an entirely new category of illness, "Mild Illnesses", just so this system can experience the light of day. Mild illnesses are never fatal, and will always pass on their own eventually, even without player intervention. Think the Common Cold, or 'Winter Worn', as I hear they like to call it in Skyrim *wink* *wink*. Again this system can be adjusted an disabled in the MCM, separately from normal dynamic diseases.

Here is a breakdown of what impacts the probability of catching a disease dynamically:
a)Type of illness: You are significantly more likely to contract a mild illness, such as a cold or migraine, than a normal disease. On the default MCM settings, for example, you are, on average, six times more likely to contract a mild illness compared to a normal disease.
b)Swimming: Being in water in an unhygienic environment triples the chance of contracting a disease or illness.
c)Weather: Cold or stormy weather can double, or triple the chance of contracting an illness or disease.
d)MCM Settings: The chance of contracting illnesses and diseases can be adjusted in the MCM.
e)Location:  You are far more likely to contract a serious disease in a crypt or dungeon. In contrast, you are far more likely to contract a mild illness in towns and cities. However, it is almost impossible to contract an illness or disease whilst inside a temple. Furthermore, certain diseases and illness can only be contracted in certain locations. For example, Greenspore can only be contracted dynamically whilst in water.
f)Diseases: Certain diseases increase the chance of contracting other diseases.
g)Time of Year: Certain mild illnesses are more common during set periods of the year.

7.New features in my conversion
I have been working on an off on this conversion for about two years and a half now. Although I originally intended this mod just to be a simple conversion with added compatibility for Dragonborn, overtime it has grown into its own thing. If you are looking for a straight conversion of Manaflow's original mod, and dislike the sound of some of my changes, you can download AndrealphusVIII's port of the mod to SSE: Diseased - Disease Systems Overhaul SSE

Anyway, what follows is a list of the changes and additions I have made...as far as I can remember (problems of working on a mod for this long and not getting on with it, my bad lol).

15 new diseases in addition to those in vanilla:
10 Mild illnesses

Gameplay Changes:

• 6 new animal loot ingredients to make poisons with.
• Dynamic illnesses now affected by more factors (water etc.)
• Changes to vanilla Cure Disease potion (now only cures diseases that haven't evolved yet) for balance reasons. In the original mod, normal , non-specific “Cure Disease” potions (the ones used to cure diseases in vanilla Skyrim) were still effective, and ensured that the player would pass the next evolution check of any disease. This always struck me as strange, as it drastically reduced the incentive to use any disease-specific medicines and potions. As a result, I decided to alter the mechanics behind them. Generic "Cure Disease" potions now only work when a disease is first caught, and before its first evolution check occurs. As such, they will have to be used relatively soon after a disease is first caught in order to take effect.
• Animals can now give more than one disease (for instance, Skeever's can now give 4 newly added diseases as well as Ataxia).
• Vigilants of Stendar can now diagnose a disease.
• Getting cured by Vigilants of Stendar will no longer immediately remove all diseases, but will instead add disease resistance for a period of time (similar to how praying works).
• If iNeed and its compatibility patch are installed, priests will also be able to diagnose and treat diseases.
• Certain diseases can only be dynamically caught on Solstheim (Chanthrax and Droops)
  

New MCM options:

• Can now change the global likelihood of catching diseases, including from animals attacks. (Note: 100% Disease resistances will still yield a 100% chance to resist, no matter what this setting is set to. If you change this setting and you are still not catching diseases, you may have another mod messing with your disease resistance. Just something to keep in mind).
• Complex Medicine Recipes
• Can hide the first stage of a disease from the magic effect list. This means it wont be immediately obvious whether you've caught or recovered from a disease. Leads to more realistic progression (after all, you wouldn't instantly know that you are ill at the moment of infection in real life), and pairs well with the new mechanics for Cure Disease potions (do you take a cure disease potion just in case you have a disease, or do you risk letting the disease worsen and having to take more drastic action to cure it?).
• Can hide notifications to simulate checking yourself. You won't be told whether a disease is advancing or receding, or when you caught a disease, if you do not know what the disease is. You will have to check in the magic effects menu to tell whether you have a disease or how advanced it is.
• Can hide the first stage of diseases to increase realism. E.g. You won't be aware of a disease until a while after you caught it.
• Potion and Medicine presence on vendors can be adjusted. (Can be increased or disabled entirely).
• YOT Compatibility. Changes in-game notifications from second person to first person (E.g. 'You're infected with Ataxia' becomes 'I think I'm infected with Ataxia'.
• Enabled/Disable weapon speed disease - One of the new diseases needs a fix for weapon speed. If you already have this fix, you can enable it. Otherwise the disease will not set weapon speed correctly (it might be increased or unnoticable). You can read more about this issue here: https://www.nexusmods.com/skyrim/mods/28456#:~:text=Attack%20Speed%20Framework%20corrects%20an,for%20yourself%20and%20for%20NPCs. Note that many mods already include an attack speed fix, and you may already have one installed unknowingly.
  

Quality of Life Changes:

• English corrections. The original mod was great, but it was quite clear that Manaflow wasn't a native English speaker. I'm from London, so I've done my best to correct as many English mistakes as possible, (e.g. in load screens) and to keep the writing style consistent with the original tone of the game. If you find anything I've missed, please let me know, and I'll get around to correcting it. 
• Mod can now detect diseases which are not built into the mod. These can be cured with Cure Disease potions and at shrines once all diseases from the mod have been cured.
• Dragonborn compatibility (Droops now has stages)
• Some bug fixes with disease animations and Sanguinare Vampiris.
  

8.Compatibility
Unlike the original Diseased mod, this conversion is compatible with all other mods that add new diseases. Whilst they will not worsen and improve like the diseases built into the mod do, they can be cured by praying at an altar or taking a generic Cure Disease potion once all other in-built diseases have been cured.

iNeed is now also fully compatible with the use of the patch in the download section. Stomach Rot worsens and improves in stages like other diseases in this mod. Gutworm can now also be contracted from uncooked meat. There is also a book specifically written for Stomach Rot which allows for the creation of a medicinal cure.

As for things like Realistic Needs and Diseases, make sure to place Diseased Remastered AFTER/below whatever version of R&D you are using in your load order, and download the relevant patch from the optional files.

Base Sunhelm is compatible. However, its disease module is not. 

About Last Seed Patch: This makes it so the diseases from Diseased affect vitality. Fatal diseases reduce vitality by a lot (this is now how they will kill you, so make sure you have "death at zero vitality" enabled or diseases will no longer be fatal). Non-fatal diseases will only reduce it slightly. How much each disease impacts vitality also depends on how advanced each disease is. Keep in mind low vitality reduces disease resistance, so it will be harder to cure diseases if you are unhealthy.

There are a set of instructions in the description of the patch file that you must follow. This includes disabling "Shrines Increase Disease Resistance", "Priests Cure Diseases" (Use Diseased's option for this instead if you want this), "Additional Diseases" and changing "Cure Disease Potion Behavior" to "Generic" in Last Seed's MCM. Unfortunately, the additional diseases added by Last Seed are not supported at this time. However, a lot of them are already covered by this mod (as well as a lot which aren't in Last Seed), so it shouldn't be too much of an issue.

Other needs mods should also work fine, as long as they do not change how diseases work.

I am not sure about survival mode. I think it will work, but haven't had the chance to test it. If anyone has tried it out with this mod, let me know how it runs.

Mods which directly change the entries for animals may not be 100% compatible. To allow animals to give the player more than one disease, I edited the entries for Skeevers, Bears, Sabre Cats, Wolves, Slaughterfish, Boars, Ash Hoppers, Chaurus, Draugr, Foxes, Frostbite Spiders, Hagravens, Trolls Mudcrabs and Ash Spawn. Issue should be solved by a merged patch.

Also made changes directly to leveled lists of two specific vendors in Solstheim to ensure a relevant book would appear there. This change is really not that vital, so if there is a conflict related to "DLC2MerchantTelMithrynElyneasChest "Chest" [CONT:040177BE]" or "DLC2RRMiloreVendorChest "Chest" [CONT:0402501C]", let the other mod overwrite my mod or create a merged patch.

Here is the entries from the original game that this mod edits directly (if you are into mods and want to know whether your mod id compatible):


Special thanks to:
manaflow - Original creator
Glanzer - Bug testing and patches
Darklustre - Creative input