On: An injection of magma under Norris Geyser Basin

[Jeema101]

I mean, that's kind of what HIV was up until the mid-late 90s anyway. No symptoms for years and then nearly 100% mortality.

It's killed millions but still hasn't wiped out civilization.

[magduf → Jeema101]

HIV didn't spread very quickly because it required fluid transfer (and usually sexual, even kissing generally didn't spread it). It's hard to have an "outbreak" when a virus is so difficult to spread between people.