From what I understand so far about this prophecy, death, assassination, and plagues of unknown origins (although, from everything I see, it'll be of divine origin) will strike the wicked, the ungodly, the evil, and the corrupt.  But specifically it will touch those who are blatantly, and defiantly unrepentant.  All of these deaths, including the plagues, will be very targeted, and not contagious at all (at least that's what I am seeing), 100% incurable and completely unstoppable, quick, and unquestionably deadly.  The diseases will rot their interiors, and produce boils, and lesions, and other nasty visible signs that it's there.  Everyone who catches it will die, period.

On the flipside, these diseases, and mysterious deaths. will not touch ANY believers in Christ, nor anyone who is saved.  It will not come near them.  In other words, death will not touch the righteous, nor will sick people be able to transmit these plagues to believers as the diseases will come directly from God as judgment against the blatantly unrepentant.  Now, as for those who are unsaved, who are not counted among the blatantly unrepentant, it's not clear if they are protected as well.  That's kind of a gray area in all this.  All I can say is that, if someone is firmly, and unwaveringly unrepentant, they will absolutely catch this disease, and they will die quickly, with no hope of being saved.  The willfully unrepentant will be severely judged in this upcoming time period, and they will have no hope of escaping it.

This great death that will sweep the world will also strike innocent children, not for anything they've done, but for what their parents forced them to do.  Think of it as collateral damage caused by sinful, unrepentant parents who did things that led to their deaths.  So their deaths won't be the fault of their spiritual condition (like it will be for those listed above), but rather it'll be a consequence of thier parents, who have leadership, authority, and responsibility over them.

Update (2023-01-26): I've changed the title to be a bit more general in regards to this great dying off that's coming.  Especially since a significant portion of those dying will be doing so, not because of what they've done, but because of what other sinful people have done to them that led to their deaths.