Above is a rather odd song about the Black Death. I'll warn you, the "fleas on rats" chorus is liable to get stuck in your head, I know it drove me nuts as I merrily hummed it for a day or two.
It's from a series of educational songs produced to introduce various subjects in high school (at least that's what I gather from the comments). I don't know how well they work, but I imagine they are pretty good for kicking off a lecture on a given topic. People younger then me fondly remember Schoolhouse Rock from Saturday mornings, I suspect the generation now in high school will have fond memories of these.
It is from a YouTube channel called historyteachers (History for Music Lovers). If you go there you can find more of their video efforts.
Along with the Black Death one, I quite liked Copernicus ("Because" by the Beatles).