Kharaa Bacterium

https://subnautica.fandom.com/wiki/Kharaa\_Bacterium

Kharaa was brought to 4546B by the Precursors in an attempt to find a vaccine, as they had established outposts within The Crater. It is stated in Precursor data that the Kharaa bacterium has killed over 143 billion individuals over the course of time since its discovery, but the data is likely to be around 1000 years old. 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 its 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, which cause 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 an increase in aggression in its 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 around 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 disable 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 had been exposed to the unstable variation of Enzyme 42 for prolonged periods of time, 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