It's also worth noting that Europeans are not at the top of the food chain in terms of disease resistance. Various European powers raised a flag on New Guinea, but they never successfully colonized it. It's a cesspool of disease, and Europeans never managed to do more than establish a few trading posts on the beach.
This arms race meant that the diseases were tough, the Euros were tough, but those races who had been spared the arms-race of filthiness were sitting ducks to the Euro super diseases.
It could be that Euro-african civilisations were more effective at cultivating new diseases thanks to the crossover between animals and humans.
http://en.wikipedia.org/wiki/Domestic_animals
Guinea pigs and llamas seem to be it for the new world. Whereas the Europeans had a vast list of animals available. They'd live in tight confines with pigs and chickens and cows during long cold winters - fabulous creatures and circumstances for cultivating new strains of disease.