Cruise ships, unfortunately, are prone to exacerbating any sort of disease outbreak due to their nature. For instance, back in 2020, aboard the Diamond Princess, Covid spread with an R0 5x higher than usual.
If anything, it’s surprising that more people didn’t get infected by this, which shows just how poor hantavirus is at human-to-human spread.
To my knowledge, there are infinite expansion models that allow for the formation of a “relaxed” void where a fairly limited number of Boltzmann brains would ever form.
The recent discoveries about the nature of dark energy also seemingly suggest infinite expansion isn’t going to happen, so that’s another possible solution.