It has been theorized by William H. McNeill in Plagues and Peoples that the silk road, the overland route from The East, that brought the Black Death to Europe.

He speculates that it was Venice, the hinge of Europe, (and the title of one of his books), that radiated this disease throughout the western world.

In this, he illuminates the role transportation always has, and more importantly, still plays today in the spread of disease. Jets can bring ebola fever, or some other highly contagious disease to North America in a matter of scant hours.

Rather than religion, or ignorance that brings us disease, it is technology and intelligence.