It is stated in Precursor data that the Kharaa bacterium has killed over 143 billion individuals over the course of time since its discovery. It is possible this is not the true death count as the PDA entry only lists these as "Confirmed Deaths" which could imply further dead beyond what was known. Their core worlds were quarantined off, and research facilities such as the one on 4546B were created to find a cure. After a Sea Dragon Leviathan damaged the Disease Research Facility in an attempt to retrieve its offspring, the previously contained Kharaa bacterium was released onto the planet. This decimated the planet's ecosystems, as much of the life on the planet died due to the bacterium's immuno-repressive behaviour and genetic corruption. This prompted the Precursors to initiate their emergency quarantine: activating the Quarantine Enforcement Platform. The Quarantine Enforcement Platform shoots down all approaching or departing spacecraft to prevent Kharaa being spread to other planets.
The PDA estimates that Kharaa incubates in two weeks and quickly kills it's host after it reaches a substantial infection level. It accomplishes this by shutting down the immune system (already making the infected host susceptible to other diseases) and causing genetic mutation to the host's DNA, and causing alterations to the body structure, eventually leading to a total shutdown of the organism due to its inability to keep functioning properly. According to Precursor data, the bacterium is capable of entering the body through the skin, and causes in increase in aggression in it's host.
Warpers were created to keep the levels of Kharaa to a minimum, to do so they will attempt to kill infected fauna, in an effort to control the spread of the bacterium. This however seems to have been ineffective as Kharaa is still ravaging the planet a little under one thousand years after it was initially released.
Ryley Robinson is infected with Kharaa, though he only becomes aware of it after attempting to disable the Quarantine Enforcement Platform, as the deactivation terminal will tell him that he is infected and therefore cannot use it, thus forcing Ryley to secure a cure in order to leave the planet. The infection only becomes noticeable when Ryley reaches the Disease Research Facility and is prompted by the PDA to perform a self-scan. At this point it will warn him that the infection is reaching a critical stage and his skin breaks out into glowing green cysts. The same happens to Medical Officer Danby in Lifepod 12. However, unlike Ryley, Danby developed visible signs of infection within three hours. The reason for this is unknown, although the infection rate most likely varies depending on the individual. However, it is also possible that since Ryley was exposed to the unstable variation of Enzyme 42, it slowed his progression, whereas Danby was not, and Kharaa quickly spread throughout his system.
The Degasi survivors were also infected at one point. Bart Torgal attempted to find out what it was, although he was unsuccessful as Marguerit continually brought specimens for him to study near death or injected them with Transfuser serums, making them unreliable test subjects. However, he was able to deduce that every organism was infected, as well as taking precautions to ensure the Degasi crew's survival. However, upon the destruction of the Deep Grand Reef base, Bart fled to the Safe Shallows and began noting the details of Kharaa on him, and eventually flees to the Floating Island, where he makes his final log and most likely succumbs to the bacterium.
If an infected creature is placed inside an Aquarium or Alien Containment, the creature will infect the rest of the creatures inside soon after. However, this is purely cosmetic and has no impact on gameplay.
The player can scan fauna that have been scanned previously to check if they are infected with Kharaa. When scanned, a creature can be identified as infected or not by the screen on the Scanner saying "normal" or "infected". The player can also scan themselves to monitor the bacterium's progress in their body.
It seems that the only way to cure Kharaa is with Enzyme 42 produced by the Sea Emperor Leviathan and its young, as shall be shown by creatures being cured by the enzymes in the Sea Emperor's aquarium.
Peepers are able to use the Alien Vents to take small amounts of Enzyme 42 back to the surface, spreading the enzyme's effects throughout the world. This method is the sole reason why some life has managed to remain immune, and possibly why Ryley, and some creatures by extent, are able to survive some time after being initially infected.
The Sea Emperor Leviathan and the Warper are immune to the Kharaa bacterium, as they both play a role in eliminating it - with the Sea Emperor Leviathan producing Enzyme 42 as a countermeasure, and the Warper being the result of its biomechanical adaptations implemented by the Precursors.
Kharaa manifests itself in bright green cysts, along with similar colored veins spread throughout its host. The cysts start out as small protrusions, however, as time goes on, the cysts will grow larger and glow more strongly, signifying the organism is close to death.
Data Bank Entries
You have been infected with a previously unknown, waterborne bacterium. It is currently multiplying in your bloodstream. Estimated incubation time: 2 weeks.
Your immune system is currently combating the infection at low efficacy. You may already be experiencing flu-like symptoms and skin irritation. These will likely be exacerbated as the bacterium takes hold.
Your immediate priority should be abatement and eradication of the infection.
Discovery: First encountered during routine network expansion on outer worlds.
Pandemic Development: Network error resulted in routine quarantine procedure failure. Contagion was uploaded to, and spread quickly through, the core worlds. Confirmed deaths: 143 billion individuals.
Bacterial Mechanisms: Attaches to healthy living cells and mutates the basic genetic structure.
Symptoms: Stage 1: None. Stage 2: Gradual immune system failure. Stage 3: Unpredictable alterations to biological structure. Stage 4: Complete shutdown of executive function.
Emergency Steps Taken: Core worlds quarantined. Bacterial samples distributed to isolated disease research facilities for vaccine development.
Treatment procedure: Unknown.
|Specimen with Symptoms of Unknown Infection|
This organism is displaying signs of an unknown bacterial infection.
WARNING: May be contagious. Avoid. Do not under any circumstances consume the flesh.
Scans indicate this infected organism has recently come into contact with a unique enzyme which has counteracted the most debilitating symptoms of the disease.
- Cory Strader and Tom Jubert have said that Kharaa from Natural Selection 2 is a mutated form of the Kharaa in Subnautica.
- The texture of Kharaa's cysts on the player will be limited only to the hands, since these are the place with visible skin on the player.
- In the original story script, the Kharaa was a bacterium developed by the Precursors.
- Despite symptoms of Kharaa occurring after a few weeks of contracting it, Danby managed to develop cysts within a few hours of infection.
- The former name for Kharaa Bacterium was Carar Bacterium. It was later changed to match Natural Selection 2.
- In Mongolian, Kharaa means "Curse / to curse," which ties some connections to the game.
- Kharaa seems like a spinoff to the common disease of swimmer's itch, as they both cause severe skin irritation, and the appearence of small blisters.