Reddit mentions of A History of Immunology

If I may jump in here, /u/Mycd is making a similar argument to Jared Diamond in Guns, Germs, and Steel. Though I am not sure about the claim that livestock were a significant source of disease. I know that they were a significant source of vaccination in the 18th century, but disease? Zoonotic diseases aren't usually small pox level variants (except for exotic ones which emerge well after the Columbian exchange).

There is a history of continual exposure to the major, and quite deadly, pathogens in Eurasian history that were the subject of medical inquiry from about 1000 CE onward; Chinese and Indian physicians, for example, experimented with blowing the dust from dried scabs of plague victims into the noses of people who had not gotten sick yet in order to inoculate them. It didn't work as well as modern science would have liked - the Black Death claimed tens of thousands of lives in Cairo alone - but it was better than nothing.

In Diamond's book, he makes the argument that since Eurasian trade routes were roughly east-west, the pathogens had similar enough environs - and continual human hosts - to survive and even mutate. On the other hand, Diamond points out, there was no equivalent to the Silk Road in the Western Hemisphere, thus preventing continual human-to-human transmission necessary for viral or bacterial mutation to the degree in Eurasia. Also, the fact that different latitudes often brought wildly varying environments, hampered potentially deadly plagues from emerging on such a vast scale in the Americas. He doesn't say, though, that Mesoamericans or other major empires didn't have plagues - they did - but compared to Eurasian ones, they were relatively weak or mild.

Other sources: Bernard Lewis Islam: From the Prophet Muhammad to the Capture of Constantinople

Arthur Silverstein A History of Immunology

Jared Diamond Guns, Germs, and Steel