Well, health care has improved a bit since then. Mind you, it is important to note that what we think of Black Death was really a whole host of different plagues all at once - bubonic, hemorrhagic, and several others, alongside the usual ails of the time, yer choleras and their pals. It was a massive viral soup which it infested into.   But I suppose it wouldn't help your frame of mind to know that not only does Black Death (well, bubonic) have around 15 victims a year in the USA currently(its far more common in Asia and Africa), there are signs of it becoming drug-resistant in places. But it has a 75% or there abouts mortality rate.   The big disgrace in all of this is that there are almost certainly people in Africa who are dead now from this outbreak who should be alive if someone had put human need over profit. Theres been drugs believed to aide Ebola since at least 2004, and I strongly suspect since 1975 (when the European researcher infected with it the next year was cured!). As soon as it manages to infect a rich European or American, bet your bottom dollar a cure is "miraculously" found.