Genoa and barcelona were seriously affected by the black death. why do you think this was so ?

Genoa and Barcelona were major port cities in Spain during the time of the Black Plague. Diseased rats traveled on board ships which was the main reason the plague spread like wildfire- the rats were able to move from place to place. Because so many ships docked at the ports the rats were able to infect people. Citizens at this time were so used to getting bit by things that they didn't even take notice of the bite until they started dying. 

Shouldn’t there be a graph?