Theory on what the Kahara infection is - SPOILERS

So I've had a theory for a while on what the Kahara infection is. To be fair, it's a tad unrealistic in the game given that an alien species so advanced likely would have found a cure for most diseases or even hardened themselves against it, on top of the idea that it was just a random enzyme from a creature that was the cure, but these aliens somehow couldn't produce it in a lab. With nanobots that can target bacteria and kill them, something akin to the DRACO cure, antibodies that can be deposited from creatures via genetically engineered host (I.E. such as with regeneron and mice), and a host of other options, it would be possible in the future to cure virtually all major diseases of almost any type, if only with nanobots, so why this is something they can't seem to cure seems a bit far-fetched, UNLESS, the virus has some sort of extreme effect beyond that of a normal disease. It would need to be something extremely advanced and complicated, like a nanobot or engineered virus for example, that this enzyme, which would need to not just be an enzyme (perhaps a symbiotic bacteria that is absorbed in to the host and produces the enzyme), just so happens to be able to break down, and quickly I might add. So, what could it, and the cure possibly be? I have a number of theories!

First, the infection seems to glow in the body, which is exceptionally rare for any disease, although could be explained by the fact that it is bioluminescent. So, this bacteria or perhaps an algae, or combination of various bacteria and other things (such as viruses, microscopic creatures and nanobots; malaria for example is a combination of diseases including bacteria and viruses), needs to glow, and this requires it to be more complex than most infections. This is easily explained by the fact that everything in the game is bioluminescent, and, it may glow deliberately to attract creatures in to eating it, thus causing it to spread. It aslo could be radioactive. Second, we have to wonder why the super advanced aliens couldn't cure it. It could be hubris in part, they didn't see it as a threat until it spread so far and fast that they finally responded to it too late, thinking they could cure everything, or that their cure was worse than the disease and ended up killing everyone by mistake (I.E. the nanobots went haywire and turned them in to grey goop, or just didn't work right), but there are other explanations that perhaps could be combined with this. On the one hand, it could mutate so quickly that even after they come up with a cure it just mutates, and this could explain how it's so powerful and could mean that no strain of Kahara is even the same, so there is no vaccine that can be developed for it, only a very broad mega-cure that targets all forms of it, which would be harder to develop. Even nanobots might have a hard time focusing on too many different forms of infections, and if programmed to go after too broad a range of things, could result in the grey goop problem, where it targets healthy cells and thus kills the host. Any kind of nanobot would need to be focused on specific things, for fear of it killing healthy cells. Even worse would be if the viral or bacterial cells somehow mimicked the DNA of the host, and thus made it possible to trick such a cure in to going after the host, which would ironically make it too advanced of a cure for it's own good. Essentially if the nanobots were programmed to go after altered forms of bacteria, it may be "tricked" in to eventually going after healthy host cells.

The bacteria also could leave behind long lasting permanent effects, so even after it's cured or killed, the lasting side-effects persist. This is in my opinion the most interesting explanation, as the virus may actually alter the host's genetic material on a fundamental level, so much so that even with a cure, the damage is done and irreversible, and so this is what effectively made it incurable on a living host even for an advanced alien species. Viruses in general are known to change animal genetic material, and humans have as much as 8% of their DNA as "Junk DNA", which is largely from viruses, which is from permanent changes to the human DNA structure caused by viruses. In theory if the changes were great enough, this could fundamentally alter the host, and make it impossible to cure, as the only cure would be to get brand new DNA which would be, hard to do even for an advanced species. Something to neutralize this change in the DNA as the body slowly tears itself apart and mutates, possibly with glowing cancerous orbs, would be needed. Cancer too is caused by a change in DNA and, some viruses are known to cause cancer. So even if a cure is discovered, the disease may essentially cause cancer or mutations so sufficient it would kill the host even if the virus-bacteria-something hybrid was killed. As it glows, it could have radioactive materials in it, and with it being mutagenic this could explain the bacteria's rapidly and constantly mutating genetic structure that would make it hard to cure, but it could also cause cancer or something like it, and bind with DNA, so even after it's cured, it's fundamentally changed the host's DNA to where the only solution is to abandon the host body or change it somehow, which would be hard even for nanobots to fix, and is basically the plot of the second game. The enzyme could come from another infectious bacteria but that is actually positive for the host (humans have bacteria in their gut, for example to help them digest food), and thus what the animal provides is not just an enzyme which cures the disease, but another infection to fight that infection, or good bacteria, that rapidly spreads through the host and neutralizes radiation and/or whatever effect of that virus. The mutations would effectively persist in the DNA, although, they wouldn't do anything, effectively becoming junk DNA. The good bacteria could also stave off the effects, and even reverse them to some degree, and kill the host virus.

Of course, the virus itself could essentially not be a virus at all, but a nanobot plague. It's possible for nanobots, tiny microscopic robots, or nanoscopic, to infect the individual like a virus would, however it would be a bunch of tiny machines, that then start taking over the body. Even if you engineered your own nanobot cure for it, it may be designed to fight it, and so only some kind of enzyme which breaks down some critical element of this nanobot virus would actually be able to fight it. Nanobots to fight nanobots might fail, and so the only thing that might work is a special enzyme designed to break it down which, for some reason happens to work. Most nanobots would in theory be made of carbon and thus dissolve in materials like anything else made up of carbon, including humans, and so it would be difficult to come up with, but not impossible, for an enzyme to do it. One issue could be that while the enzyme could be made in a lab, it couldn't be made in mass quantities, and the cheap and easy way to mass produce it is only with a bacteria that they don't happen to have or know how to activate. So isolating the enzyme by itself could be extremely difficult to do, but using an organic entity to mass produce it would be easier. Self replication is a powerful tool and, just like how brains mass produce themselves via reproduction but a computer as powerful as a brain would be extremely difficult to make, an organic solution would be cheaper. Humans self replicate without any kind of technological input and so, organic computers are cheaper than mechanical one's, but also harder to design, if not nearly impossible. It's also possible that most of the computers used by said advanced civilization were organic in nature, essentially robotic animals, and thus they got infected and it wiped out the society not by just the disease ,but by destroying most of their technology.



With a combination of many of these ideas in to one big idea, a combination of hubris, a quickly mutating virus-bacteria hybrid, something to do with nanobots and so on, it may actually explain, more in depth, why such an advanced species couldn't come up with a cure, but it was randomly generated in nature. While it is just a story plot point, I've thought about it quite a bit in depth over time! So, what do you think?

TL;DR: Virus is too complicated for a more intelligent species to cure, but miracously cured by an enzyme a telepathic creature just happens to have out of nowhere. Convenient macguffin? OR! Could there be an explanation! I say nanobots and a multi-tiered constantly evolving virus, mixed somehow with nanobots, perhaps designed as a weaponized plague to wipe out another species that accidentally turned on the species who invented it. Idk.