I can't see any possible causation between the Black Death and the Little Ice Age. However, I could believe that the Little Ice Age caused more rodents to move inside houses and thus had closer contact between rodent fleas and humans. That could have been causative. Wild rodents are the natural pool for Bubonic Plague. We have it in the rodents living in the Sierras. Every year somebody comes back from hiking the mountain trails and comes down with it. Fortunately, very few of those are pneumonic-phase infections but CDC still tracks down everybody who was on an airplane with them and has them checked out. Very few of these people have rodent infested houses, so the normal-phase of spread is not possible.

I guess I might have a problem with Covid19 because I'm immune-suppressed. I have to balance infections against brain lesions. Doing pretty well so far. I heal pretty well and actually rarely get the histamine reactions when I get a cold. So my system seems to still be able to fight off viruses.