Zenar Virus/Z-2
Zenars are an invasive predatory species that originate from the Zenar Virus. They are responsible for bringing the world to ruin in only four short years after they arrived. The Zenar Virus originates from another world/dimension. After some study, it is revealed that the Zener Virus is actually a run-off strand of a different virus called Z-1.
The Zenar Virus is mainly attracted to kids but if there are no kids in the area the virus will reanimate adult corpses and turn them into the kid version of themselves and infect them. It is unclear why the Zenar Virus does this but it may be due to the adoption effect that Zenars have worked best for bodies growing up. Z-2 also only affects those who resemble humans.
Since the Zenar Virus can infect dead bodies even if they are burned to ash or disintegrated by their atoms, killing children just because of an outbreak is heavily looked down upon, even if it does slow the infection down.
Since Zenars are extremely deadly and the virus is even harder to study than it is to kill a Zenar, there is little information about the Zenar Virus. There is one thing of interest that is seen as either a final hope for wiping out the Zenars or seen as the sign of everything ending. Z-2 shows signs that it must have a real physical form; one Zenar that controls the virus. That Zenar has yet to appear but seeing as that Zenars seem to worship them as a God, it can probably control all Zenars, even the Alphas. It is not known if this Zenar, upon being killed, will stop the entire Zenar infection or a new one will just take its place but the more research is done the more the first option seems likely. The biggest problem about this is that no one knows just how powerful or different this Zenar is. One Zenar pissed off enough can destroy a planet the size of Earth with one punch and it is clear that Zenars seem to always be holding back what they are truly capable of. This Zenar, named Z-G or Nerfella, may change that or may not be restricted. If this Zenar ever comes into existence, can we kill it may be the least of our worries.