Diseases in 5e

The perils of having an above-average Constitution - everyone in my household except me is sick! Even my doughty Shetland Sheepdog is out of sorts. So today, I'm exposing you to my stray thoughts on diseases in 5e.

Here's my controversial take: I think that RuneQuest, and its setting of Glorantha, has the best fantasy take on diseases I've seen. In RQ, diseases are spirits that possess and weaken you. They wear down your attributes and can cause permanent penalties. However, in RQ you can spend money on training to increase ability scores. A disease is rough, but it plays out more like energy drain in old school D&D. It's scary, but if you survive you can recover what you lost.

For 5e, I'd like diseases to feel more like curses. They're categorized together in the SRD and I think that makes sense. I like the idea of a penalty that sticks to your character over time.

I don't want the rules to turn into a health simulator. We've all been sick and are familiar with the rhythm of slowly feeling worse, hitting bottom, then (hopefully!) slowly recovering. I don't want to get into that level of detail. I'd like the disease to be a condition that is on or off.

I'd also like a disease to be a hindrance without shutting down your character. The condition it applies should alter how you play and pose another challenge in an adventure. I want diseases to feel like an obstacle.

Finally, diseases that mimic real world plagues can focus on exhaustion levels. I want the fancy diseases I stat up to reflect weird, magical, or oddball effects you might run into while hexcrawling.

Disease Stats

A disease has three elements: Exposure, Duration, and Effect.

Exposure gives the check or save DC to avoid the disease and the conditions that set it. A disease might have more than one DC to reflect serious or minor exposure.

Duration explains when to make checks to see if the disease lingers or is cured. If special cures exist, they are explained here.

Effect is what applies to a character while they have the disease.

That's it! Let's look at an example. You'll notice that this disease is not fatal. That's intentional on my part. There are plenty of examples of diseases that can kill your character. I want ones that are a little weirder and more curse-like.

Creak Lung

This disease is caused by exposure to the moldy air found in fungoid lairs. It leaves its victims with a persistent, loud cough. Each breath they take creates a faint creaking noise, as the fungal infection in their lungs creaks and moves.

Exposure. When you take a long rest after spending more than an hour breathing the air in a fungoid lair, or 24 hours after you do so, make a DC 10 Constitution save. On a failed save, you contract this disease. Alternatively, you or someone who treats you can make a Intelligence (Medicine) check in place of the save with the same DC if they treat you during the long rest.

Duration. While you have the disease, repeat the save as above after each long rest or 24 hours after your last check, whichever comes first. If you succeed, the disease ends.

Effect. A small colony of fungoid spores grows in your lungs. You have disadvantage on all Constitution tests. Owing to the background psionic activity of the fungoids, you cannot hide from such creatures as the colony psychically broadcasts your location. However, you do gain the ability to hear their telepathic communication and can speak with them while you are infected.

Each time you finish a long rest, the DM rolls a d20 in secret. On a 1, a small colony of fungoid spores takes root nearby. Within 2d6 days, the first fungoids - typically 1d6 shrieking fungoids and 1d4 violet fungoids - emerge to create a colony. These fungoids recognize the creature that carried the spores that created them. They might consider this creature their creator, or they may be driven to sacrifice them and liberate the spores within them.

If you die while infected, the colony described above grows from the corpse, emerging in 2d6 days.