Disease in D&D

Diseases suck. Both in life and in D&D. It's not an enemy one gets to fight traditionally, so sickness comes down to a save or be gimped for a period of time. This is why we don't see a lot of disease in RPGs, it's just not a fun mechanic most of the time.

But what if it was important for story/lore reasons to have disease? What if it was a facet of the campaign, and there was the expectation that people would be sick sometimes, or that the party might have to slow down and rest, or that one would need to seek out or hire a healer as a resource sink? What if we really wanted to add diseases into our game, how would we go about it.

Here's some ideas for sickness / disease that I've been kicking around. We're not going to deal with transmission, but we will deal with what effects it has, and how we can navigate an illness that has set in. For our example, we'll be using 5th edition D&D.

First, a list of possible effects

• Lose all your existing hit dice
• Do not gain hit dice
• Cannot gain HP other than from magical healing
• Cannot take a long rest
• Cannot take a short rest
• Speed halved
• Speed 0
• No attacks or spell casting
• Take damage every day
• Lose stats - flat
• Lose stats - half
• Lose stats - daily
• Disadvantage on physical checks (Str, Dex, Con)
• Disadvantage on mental checks (Int, Wis, Chr)
• Fail physical checks
• Fail mental checks
• Death saves [die on failure]
• Condition worsens automatically by 1 step each day

There are the tools we have at hand to hinder a person who has been stricken with illness. You might find some other to add to the list.

Rule 1
Diseases have a con save DC that one makes to avoid contracting the disease, and different levels of sickness for those who fail. If you fail the save, your disease starts at the step/level indicated by the die.

Rule 2
When you are sick, you lose all your existing hit dice, cannot gain any, and cannot gain HP except by magical healing until the disease passes.

Rule 3
Every day of your illness, you can repeat the initial save. If you roll a 20, your condition improves by 4 steps. If you pass, your condition improves by 2 steps. If you fail, the condition remains the same. If you roll a 1 or fail your roll by 10 points or more, your condition worsens by 2 steps.

Rule 4
Your behavior / treatment adjusts your save. If you are getting bedrest and attention from a healer, you get advantage on your save. If you get bedrest and care from a non-healer, you make your save normally. Anything less and you make your save at disadvantage. If you push through your illness and don't rest, you automatically fail your save and you roll 3 dice to see if any of them show up as 1s (worsening your condition by 2 if you do).

Disadvantage works normally, so if you have a condition that gives you disadvantage on your saves, and you are being tended to by a healer, you make your saves normally.

You always get a save. Even if you have a condition that says you fail physical checks, you still get to make a con save vs. your disease.

Rule 5
If your Strength, Constitution, or Wisdom/Willpower reach 0, you die. If you are required to make death saves, and fail them - you die. If you succeed and your condition does not improve the next day, you make death saves again.

With these rules in mind, I'm going to give a sample disease, walk through how it might go, explain some theory behind crafting diseases, and then detail a few more diseases for completeness.

Generic Illness: DC 10
9 - No long rest
8 - No short rest
7 - Physical checks at disadvantage
6 - Speed reduced to half
5 - All stats lose 1 per day
4 - 1d8 damage per day
3 - Physical checks automatically fail
2 or less - No move, attack, or spellcasting

With this sickness, a character must pass a DC10 con save to avoid all effects (aka, they are asymptomatic or overcome it right away).

If our character had rolled a 7 on their save, they are infected and feeling pretty bad. They've lost all their hit dice and can't gain any more. They can't benefit from a long rest or a short rest, and any check they need to make that relies on Str, Dex, or Con is made at disadvantage.

The next morning when they go to make a save, they roll a 1. This is bad. Their condition worsens by 2 steps, losing them half their speed and 1 point from each of their stats per day, including this morning. Their illness has gone from annoying to potentially life threatening. If their condition does not improve, they will lose stats until they die.

The next morning, they go to make their DC 10 con save again and score a natural 20! With excellent luck, their condition improves by 4 steps, bringing them from a 5 to a 9. They're still down 1 point in all their stats, but they're feeling much better, their speed is at full, they can make all their physical checks normally, and they can even take a short rest!

For the next 3 days our character fails their save. They're much better, but the sickness is lingering just enough to keep them from regaining HP, HD, and long rest abilities.

Finally, on the 7th day they pass their save and are free and clear from the sickness! Hurray.

How to build a disease

Let's start with the worst case scenario. If you get a really bad case of this sickness, what happens? If it's potentially lethal, then it should have damage, stat loss, or death saves involved somewhere. Without those, your character won't die from the illness - although they might die because they were unable to recover hp or abilities.

Next, we set a DC with the assumption that the general population has 10 or 11 con and isn't proficient in con saves.

A DC of 5 is a mild illness. 80% of people won't catch it, and it has fewer possible steps so even if you roll very poorly just a pair of successes will see you healthy again.

A DC of 10 is a serious illness. About half of all people who catch it will contract some symptoms and recovering from this is much harder. A character has about a 50% chance of improving. If a DC10 disease has many steps, then a portion of the population will be very sick for a time as they slowly claw their way back up.

A DC of 15 will be contracted by most people who will be sick for a while, and a DC of 20 is apocalyptic - everyone is sick and nobody is getting better.

Lastly we look at the number of steps. The more steps, the longer the path to recovery. Fewer steps indicate something that blows in an out more quickly.

Example Diseases

Splinter Skin - DC 10
8-9 - Speed reduced to half
7 - No long rest
6 - No short rest
5 - Disadvantage on dex checks
3-4 - Dex reduced to half
2 or less - No move or attack

A frustrating skin condition that causes pain at the slightest touch. Mild cases slow you down, severe cases are debilitating. Recovery takes a few days.

Malaise - DC 18
13-17 - No long rest
11-12 - No short rest
10 or less - Speed reduced to half and disadvantage on mental checks

This disease won't kill you, but it will slow you down and make life difficult. Half of all people exposed will come down with the worst version and need 2 difficult successes to be free of it.

Hemorrhagic Fever - DC 10
5-9 - 1d4 damage daily, speed reduced to half, disadvantage on mental checks
4 - 1d6 damage daily
3 - 1d8 damage daily
2 - 1d10 damage daily
1 - 2d6 damage daily
0 or less - 3d6 damage daily

With a DC of 10, half the population will be sick. Half of the sick people will be taking 1d4 damage every day (a mild version), while the rest of the people have increasingly damaging sicknesses. Those with negative con saves might even score a 0 on their roll and suffer terrible, terrible damage every day. This disease moves fast with people dying or recovering in just a few days. PCs are unlikely to die from this unless they are low level or deeply unlucky.

Wasting Disease - DC 15
2-14 - All stats lose 1 per day
1 - All stats lose 2 per day
0 or less - All stats lose 3 per day

This is a very serious illness. With it you are mostly functional, but slowly dying. Your save will get worse and worse as time passes from the loss of con. On the other hand, unless they're a sickly character to begin with (negative con mod) the disease doesn't linger.

Influenza - DC 15
12-14 - No long rest
11 - Speed reduced to half
10 - No short rest
9 - Physical and mental checks at disadvantage
5-8 - Fail physical and mental checks
3-4 - No move and all stats lose 1 per day
2 or less - All stats lose 2 per day

A mild case (at least a 10 on the save) is annoying, a moderate case (5-9 on the save) is debilitating. A serious case is deadly. 20% of people who come into contact with this disease will be losing stats every day while having to make a DC 15 save at disadvantage, ~15% mortality rate. Those who contract moderate or worse cases will need to pass many difficult checks to recover, making this disease quite debilitating.

The Pox - DC 10
9 - 1d4 damage daily
8 - Disadvantage on charisma checks
6-7 - 1d6 damage daily
5 - Stats flatly reduced by 1 and disadvantage on physical checks
4 - Stats flatly reduced by 2
2-3 - 1d8 damage daily
1 or less - Stats flatly reduced by 4

With boils and blisters and nasty ugly signs, this damage dealing disease is frustrating to rid yourself of and publicly embarrassing. Without a cleric around, this disease will kill many. With a cleric, this can be held at bay long enough to recover.

The Plague - DC 10
7-9 - 1d4 damage daily and disadvantage on physical checks
6 - Condition worsens by 1 step daily
5 - 1d8 damage daily and speed reduced to half
4 - Fail physical checks, disadvantage on mental checks, no move or attack
3 or less - Death Saves

Very nasty, and not at all fun to play with unless you've got Cure Disease available in the party. ~25% mortality rate.

So that's it. That's diseases and why they suck in game. If you run with one of these, the party will chill in town making saves until their PC dies or recovers. If they die to disease, it's super unfun. If they recover, they might have lost some time and resources.