@Intosh I heard about loads of "dirty Medieval Europe" stories, such as:
Nobles just pooping/pissing on the floor while dancing/drinking/eating in parties/banquets, and this is not limited to Medieval era.
Or, Medieval people in cities casually throwing/pouring feces and urinate on the streets as a way to dispose them.
Also, the famous legend of Medieval people drinking beer and ale because water was too dirty as well.
There are certain clubs in the world today that a person may go to now that due to consumption of intoxicants, people still do vomit, defecate and urinate on accident or intentionally upon effect of these substances. I do not believe the feast and party hygiene was what the typical european interacted with and even so, parties cannot be held each day as said noble would exhaust his/her resources.
It is also important to note, it is not necessary in most traditional societies to possess sewers and these sorts of you are directly near major bodies of water. The custom in many societies along major river ways is to simply stock said waste into the riverways. Mesopotamian societies had no inclination or will to create such systems of sewers or sanitation as the river provided for them. The same is to be said for most riverine communities of the Middle Ages and for some societies today. The idea of a sewage and bathing system is novel in and of itself, european medieval society possessed public bath works which in and of itself is a somewhat advanced trait in a world and custom wherein most peoples found their bathing only in bodies of natural water. Sewage in the other hand, is not necessary as the major riverways fitting Europe can provide the necessary function, as it did with Babylon or Nineveh (both at one point, cities larger than many cities with sewage systems) (no one refers to Babylon as filthy in this board, despite it being very much similar to say the medieval Rhineland).
I am not sure regarding the infection of water. It would seem to me that the consumption of beers and so forth had more to do with increasing one’s caloric intake. In agricultural societies, the acquisition of calories in the form of packed beers and such, would have the benefit of giving you a good caloric meal in drink form. Likewise, it could be the case that consumption of alcohol was simply preferred, Europe had a tradition of this going far back in time of feasts wherein large quantities of alcohol were consumed. It is also important to note, that many major societies would have done the same practices of depositions waste into riverways, including the most major early civilizations and of some societies wherein the population density was highest.
Further, we should recognize that the Black Plague was a devastation not only upon Europe. Estimations are just as drastic for China and the Mid East as it is for Europe. Purported population decline alongside decreasing birth rates are associated with the Mid East following the bubonic plague. It is possible thus to argue, that countries such as Egypt may have been more mal-affected than Europe or similarly so.
Finally, reports of european customs, do often come from sources that at best are biased. Namely, men of the enlightenment and ‘renaissance’ whose goal was to demean their predecessors for the sake of a supposed ideal and whole classical era. Many of the assertions made by French enlightenment historians have been outright disproven, especially matters related to noble custom, law and precedence. The fact that critical views of hygiene applied only to Europe, depicts the persistent historiographic cosmology of the enlightenment, that of flawed historical agitators.
Otherwise, this is an impossible scenario. Jewish inhabitants of Europe are Europeans, often genetically they are drawn to those around them and have customs similar. Certain customs of kosher habits and supposed benefits from any other ritual cleaning, will not save you from a disease such as the one that erupted in Eurasia. The same way that Europeans constantly cleaning and bathing never saved them from illness that was to them incomprehensible (European thought revolved around the notion that illness was related to how clean or washed you were, this is silliness). Even public washing, sewage and so forth did not save the Hatti kingdom from a surge in the plague on the Middle Bronze Age. The only way to avoid such illnesses is to have a very sparse population of very hardy people on the move or in very small self contained villages. Scythians for instance would be a good model for disease resistance.