> Were these diseases mostly caused by people being poor? And then they broke
> out into the upper classes?
I believe that they're caused by bacteria. However, you'll have to check on that.
That said, and all sarcasm aside, the poor are almost always subject to outbreaks of disease. They generally have more compromised immune systems, less access to medical services, live in cramped conditions amidst a host of vectors, etcetera.
The rich tend to have less-compromised immune systems, more access to medical services, and less exposure to disease vectors by virtue of their isolation. Historically, there are very few diseases indeed which preyed more on the rich than on the poor, excepting those of old age. I can't, in fact, think of one - syphillis was endemic among 18th century aristocrats, given that they had little to do but socialize and have sex, but syphillis was everywhere at that point in time.
In the cases you cite specifically, the vector, or method of transmission, of tuberculosis is via coughing; that of poliomyelitis is via coughing, person to person contact, or contact with infected feces. All of these would tend to hit the poor first and hardest, but it's hard to imagine the rich escaping an outbreak entirely.
The point I'm trying to make is that epidemic disease is not picky. There's a reason why the fourth horseman of the apocalypse, death, is variously referred to as pestilence, plague, or disease.
Marco
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> Marco Anglesio | The hottest places in Hell are reserved <
> mpa at the-wire.com | for those who, in times of moral <
> http://www.the-wire.com/~mpa | crisis, preserved their neutrality. <
> | --Dante <
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