July 29, 2016
How 'ARK: Survival Evolved' Disease Works [Updates]

The ARK: Survival Evolved patch 242 released Thursday morning introduced a new disease mechanic to the open-world dinosaur survival game for the first time. This new feature introduces the "Swamp Fever" ailment that can be picked up from Leeches and passed from player to player. Here's how to avoid catching it and how to cure it for PC and Xbox One Survivors.


Also known as Hamenteria, these nasty little creatures are ground zero for the transmission of Swamp Fever in ARK: Survival Evolved. They can be found lurking in the swamps on both The Island and The Center (guide) maps.

Note that there are two kinds of Leeches to look out for while venturing in and around swamps. The blue tinted Leech will attach itself to your body after just one hit and drain your hunger. The brown tinted Diseased Leech is the one you really want to avoid. If they attach themselves to your character's body or a tamed animal, then they become infected with Swamp Fever and can die unless the Leech is removed.

Leeches will need to be removed from players and tamed animals. Fortunately, there are a couple of options to do so. Players can walk up to another Survivor or a tamed animal and use the action button to bring up the radial menu and remove the Leech that way. Alternatively, Leeches can be burned off a character's body by standing over a campfire or cooking pot. A Leech body is not left behind to harvest with either of these options.

One option to consider when venturing into the swamps is to apply Bug Repellent to players and tamed animals. This will keep Leeches away.

ARK: Survival Evolved Leech
This Leech sucks, but not as much as a Diseased Leech. [Image via ARK: Survival Evolved]

Swamp Fever

If your ARK: Survival Evolved character does contract the Swamp Fever, it will be hit with a 20 percent reduction in stats, 50 percent movement speed increase, and a 20 percent decrease of food, water, and oxygen consumption. Additionally, you cannot simply kill your Survivor to remove the disease as it persists even after respawning, and you have to deal with a green haze clouding up your screen.

A player infected with the disease can infect other players just by approaching them. In other words, it is airborne and easily transferable, though not through walls. As such, it is highly suggested that any tribe members that are infected be quarantined away from everyone else. If you see someone with a green haze over their head, run the other way.

Tamed Dodos can also be infected, which is another vector to consider. They also display a green haze signifying they should be avoided. They can even be dropped into an enemy tribe's base as a tactic to spread disease there.

Players can reduce their chance of infection by increasing their Fortitude stat. Pumping the stat up to 90 gives an 80 percent chance of not contracting Swamp Fever. Note though this stat can only be increased by 2 points each time a character levels up.

Note PVE restricts infection only between tribe members and tribe owned animals. Opposing tribes cannot infect one another.

How to Remove Disease

The only way to cure Swamp Fever is to craft a Lesser Antidote at a Mortar and Pestle or Chemistry Table. This can be unlocked at level 20 using 16 Engram Points. The ingredients consist of 10 Rare Flowers, 10 Rare Mushroom, 5 Leech Blood, and 1 Narcotic.

The crux of the antidote is the Leech Blood that can only be gathered by killing and harvesting Leeches. That means a trip to the swamp. Players in the ARK: Survival Evolved Reddit and Steam communities are reporting better harvesting rates using a Hatchet, Direwolf, and Sabretooth.

Meanwhile, Rare Flowers can be harvested from bushes near mountain tops, cattails in the swamps, and Beaver Dams (guide). Likewise, Rare Mushrooms can be found when harvesting swamp trees and Crystal as well as in Beaver Dams. Narcotics are easily crafted from Spoiled Meat and Narcoberries in a Mortar and Pestle or Chemistry Table.

Note that Leech Blood does spoil after 3 hours, but its life can be extended to 1 day and 5 hours by placing it in a Preserving Bin or 12 days, 12 hours in a Refrigerator. The Lesser Antidote has a decay timer as well and spoils in 3 hours and 20 mintues. It cannot have its life extended by placing it in one of the coolers.

ARK: Survival Evolved Lesser Antidote and Leech Blood
The Lesser Antidote ingredients (top), plus Leech Blood spoil time in a Preserving Bin (left) and Refrigerator (right). [Image via ARK: Survival Evolved]

Server Options

Those that want to alter how Disease works in ARK: Survival Evolved have a couple of server options at their disposal. This will require going into the GameUserSettings.ini file to change as there is currently no configuration option available in-game currently.
  • ?NonPermanentDiseases=true - This will make Diseases not permanent (you will then lose them if you respawn).
  • ?PreventDiseases=true - This will completely disable Diseases on the server. (thus far just 'Swamp Fever').

Work In Progress

Studio Wildcard is continuing to tweak how Disease works and will likely add new diseases beyond Swamp Fever in future updates. What do you think of the disease mechanic introduced to ARK: Survival Evolved? If you have any tips or see anything that needs correcting, please share in the comments below.

ARK General Guides:

ARK Map Guide:ARK Taming Guides:[Image via Studio Wildcard Lead Developer Jeremy Stiegliz/Twitter]

[Edit: Updated guide based on 242.3 patch notes. Removed "back to the drawing board" section.]