Source: here.
Montezuma’s Revenge
Everybody knows that the Amerindians were devastated by new infectious diseases after Columbus discovered America and made it stick. Smallpox, falciparum malaria, yellow fever, bubonic plague, cholera, measles, whooping cough, etc : by some estimates, the Amerindian population dropped by about 90%, worse than the Black Plague, which only killed off half of Europe. Naturally, you wonder what ailments the Americas exported to the rest of the world.
Syphilis
We know of two for sure. First, syphilis: the first known epidemic was in 1495, in Naples, during a French invasion. By 1520 it had reached Africa and China.+++(4)+++
From the timing of the first epidemic, and the apparent newness of the disease, many have suspected that it was an import from the New World. Some, like Bartolome de las Casas, had direct knowledge: Las Casas was in Seville in 1493, his father and uncle sailed with Columbus on the second voyage, and he himself traveled to the New World in 1502, where he spent most of the rest of his life working with the Amerindians. Ruiz Diaz de Isla, a Spanish physician, reported treating some of Columbus’s crew for syphilis, and that he had observed its rapid spread in Barcelona.
I have seen someone object to this scenario, on the grounds that the two years after Columbus’s return surely couldn’t have been long enough to generate a major outbreak. I think maybe that guy doesn’t get out much. It has always looked plausible, considering paleopathological evidence (bone changes) and the timing of the first epidemic. Recent analysis shows that some American strains of pinta (a treponemal skin disease) are genetically closest to the venereal strains. I’d say the Colombian theory is pretty well established, at this point.
Interestingly, before the genetic evidence, this was one of the longest-running disputes among historians. As far as I can tell, part of the problem was (and is) that many in the social sciences routinely apply Ockham’s razor in reverse. Simple explanations are bad, even when they fit all the facts. You see this in medicine, too.
Tungiasis
The story of tungiasis, chigger flea infestation, is simpler and clearer. Female chigger fleas burrow into the skin (often the big toe) and start releasing eggs, which can lead to infection, sometimes even to gangrene. It looks as if they originated in the West Indies, and were inadvertently spread to the mainland by the Spanish. Tungiasis hit the crew of the Santa Maria. Much later, the chigger flea was introduced to Africa, carried in ballast by a ship from Brazil: the Thomas Mitchell, in 1873. It spread all through tropical Africa, and made it to India and Pakistan in 1899. It causes quite a bit of trouble even today, particularly in poor areas – specifically, people without shoes.
Typhus
There are two other diseases that are suspected of originating in the Americas. The first is typhus, gaol fever, caused by a Rickettsial organism and usually spread by lice. Sometimes it recurs after many years, in a mild form called Brill’s disease, rather like chickenpox and shingles. This means that typhus is always waiting in the wings: if the world gets sufficiently messed up, it will reappear.
Typhus shows up most often in war, usually in cool countries. There is a claim that there was a clear epidemic in Granada in 1489, which would definitely predate Columbus, but descriptions of disease symptoms by premodern physicians are amazingly unreliable. The first really reliable description seems to have been by Fracastoro, in 1546 (according to Hans Zinsser in Rats, Lice, and History). The key hint is the existence of a very closely related organism in American flying squirrels.
Thinking about it, I have the impression that the legions of the Roman Republic didn’t have high casualties due to infectious disease, while that was the dominant cause of death in more recent European armies, up until the 20tth century. If smallpox, measles, syphilis, bubonic plague, perhaps typhus, simply hadn’t arrived yet, this makes sense. Falciparum malaria wasn’t much of a factor in northern Italy until Imperial times…
Rheumatoid arthritis
The second possibly American disease is rheumatoid arthritis. We don’t even know that it has an infectious cause – but we do know that it causes characteristic skeletal changes, and that no clear-cut pre-Columbian rheumatoid skeletons are known from the Old World, while a number have been found in the lower South. To me, this makes some infectious cause seem likely: it would very much be worth following this up with the latest molecular genetic methods.
Conclusion
American crops like maize and potatoes more than canceled the demographic impact of syphilis and typhus. But although the Old World produced more dangerous pathogens than the Americas, due to size, longer time depth of agriculture, and more domesticated animals, luck played a role, too. Something as virulent as smallpox or falciparum malaria could have existed in the Americas, and if it had, Europe would have been devastated.