Contagion

Preview images show the traces that appear only in dev mode, not during normal play.

Contagion rewrites how Rimworld handles disease seeding and spread. Gone are the days where your colonists deep underground would catch malaria, or an ice base that hasn't seen a visitor in three years suddenly get an outbreak of the flu.

🌱 Seeding

Contagion seeds diseases: they do not just pop up randomly. Diseases arrive from outside sources, or from the environment. That trade caravan may be carrying the flu, or those raiders might be incubating plague.

Storyteller vs. Contagion mode
Storyteller mode matches vanilla Rimworld: it lets the storyteller decide when an outbreak occurs, captures that, and tries to do its own seeding within a timelimit. If that fails, you may get a spontaneous outbreak that spreads from one pawn; we follow the Storyteller's orders.
Contagion mode replaces that with constant, low-level random pressure. Any caravan may arrive with a diseased pawn that spreads to yours. A walk in the jungle might bring on cases of malaria or sleeping sickness. That wild animal you kill could be harboring parasites. It's tuned for balance, but without relying on the Storyteller, trading larger outbreaks for more constant low-level pressure. And NO spontaneous outbreaks.

🕸️ Spreading

Diseases in Contagion spread based on real-world disease vectors. Flu is airborne; keep your pawns separated. Plague spreads by fleas mainly, and can cross from human to animal. Parasites can find their way into the meat in your meals. Malaria and sleeping sickness match their vectors: the mosquito and the tsetse fly. One prefers day, the other night.

Incubation
Diseases start hidden. That pawn may be spreading flu before they start showing symptoms. That cow might have a parasite you haven't found yet. There's always risk, and you have to prepare for the first case ever pops up in your notifications.

Suppression
Contagion strives for game balance, and puts dampers on the spread as your colony gets more infected; with default settings, spread chances start dropping before half the colony gets any disease, matching Vanilla RimWorld. Or turn on "Let 'er Rip" mode, and let diseases run rampant!

Infected Corpses
Corpses can carry diseases like plague or parasites. Known corpses get shaded and can be filtered, and butchers check for anything suspicious when they cut into them. Plague is the worst though: those hungry fleas just lost their meal ticket and will be looking for some warm-blooded target to pass by. Better get that corpse to the dump before it turns, or just throw a molotov and let them burn.

😷 Counterplay

What's a good game of epidemiology without something to do to "stop the spread"? Contagion lets you fight against diseases, not just suffer from them.

Actions Matter
Get an outbreak that sleeping sickness was found? Switch your outdoor pawns to night work, the tsetse fly that carries it sleeps at night. Find an animal suspiciously dead? Inspect the body, and see if it's carrying anything. Build big rooms with separation to slow the spread of flu, or pack your colonists in a tiny barracks and watch it spread like wildfire.

PPE
That personal protective equipment will come in handy for your doctors. Wear a mask to reduce airborne spread, and good clothing will stop those plague corpse fluids leaking onto you as you cart them off. For the big outbreaks, suit up in a hazmat suit for near-complete protection, as long as you don't eat something with a parasite in it. Spacer-tech armors are fully sealed: that cataphract helmet WILL stop the flu with its glitterworld-level air filtration. Mod compatible with patches: some are shipped, or you can write your own, and Contagion tries to assume reasonable protection even without that.

🍦 Vanilla-Like

Contagion tries to replicate vanilla RimWorld and not ask anything more of you. No new diseases: we reuse plague and parasites for humans and animals (flu is still separated). All diseases work the same regarding treatment, severity and immunity. A sick animal will get tended automatically. The mod tries to not infect everyone, just like vanilla. Small colonies get a little more breathing room. Use the vanilla gear to protect yourself: that face mask really works now!


💾 Save Games and Performance
Contagion is designed to be save game compatible: safe to add to an existing save (it will take over your diseases, watch out!), and safe to remove (ask me about the filter serializing...). I recommend making backups until it's fully tested, but I haven't run into issues in my testing. It's also designed to be performance-friendly, no matter how many pawns are infected, with staggered checks over long durations.

🦠 Diseases

If you want to know how each disease works in Contagion, here's your reference:









Mechanites and Food Poisoning
These are left unchanged... for now...

Mod Compatibility
Contagion ships with patches for the following mods (with example items):
• Vanilla Apparel Expanded (scrubs, surgeon mask)
• Vanilla Armour Expanded (hazmat suit)
• Vanilla Factions Expanded - Medieval 2 (plague mask!)
• Vanilla Factions Expanded - Pirates (warcaskets are sealed for flavor)
• Rimatomics (MOPP suit)
• FashionRIMsta (scrubs, surgical mask)
• Equip Gas Masks (...gas mask?)

Source code:

Contagion is under the MIT license: you are free to use, modify and distribute copies of the software provided the original copyright and license notice is included. This mod was created with the help of AI coding tools.