Sorry for the distraction from the technology.
Agreed that cities are big incubators of infectious diseases.
And forests are a major source of emerging diseases.
Malaria was primarily a rural disease. There's more than a possibility that SARS came out of the wild.
While not generally an infectious disease, the hunter-gatherers I know had leprosy; a friend in his thirties had a couple of fingers missing, but recovered with modern medical treatment. They also had TB. They apparently have venereal diseases -- apparently because this is coming from blood tests but not examination.
True enough that diseases like smallpox went from the old world to the new with devastating effect, as also from Europe to Polynesia. In turn, diseases like syphillis -- apparently a new world mutation from yaws -- went from the new to Europe, and from there to Polynesia.
Don't know enough to speak for other parts of the world, but where I am, hunter-gatherers have long had relations with the outside, usually through their nearest neighbours. Thus hunter-gatherers were one of the sources of some of the exotic products of the trade of the Indian Ocean and the South China Sea. Through these trade networks, tobacco first entered their communities probably sometime in the 17th century.
kj khoo