We often hear about how the plague affected Poland less because of the sparse population density and the quarantining measures of Casimir the Great.
With Milan I have heard (though I could be wrong, please correct me if I am) it was in part because of programs to provide some kind of hygene to the poor, because of a good hygene in the rest of the population, the relative richness of the city, because of locking the sick in their house with their family and quarantining the city.

My question is why did a big part of Flanders (Bruges and surroundings) not get hit by the plague(or at least got affected to a far lesser degree), what preventive measures did they take, how did they do it as a trade city surrounded by a huge war and a sick empire, who ordered them to do so?
I knew they were rich, but I am interested in the juicy details.

As an additional questions why did other rich cities get affected (Venice, Florence, Rome etc...)

Thanks in advance for the answers. :)

(Sorry for any mistakes in my english, I am not native english and have dyslexia)