New World Colonizers and Disease

When the Europeans began colonizing the America’s, they brought with them disease that decimated the native populations. But why isn’t the converse true, how was it that the Europeans were able to colonize without everyone dying from disease in a land where they had no exposure and immunity to local diseases? Or were there simply no American diseases that were as virulent and deadly as thoughs brought by the Europeans. And why then if native Americans were brought back to Europe (for show or slavery), why didn’t they bring back diseases that could had swept across Europe?

I suggest you read Guns, Germs and Steel by Jarad Diamond.

IIRC, it was claimed that Syphilis was brought over from the Americas. Voltaire made this claim in Candide, at any rate, and I’ve alternately heard it reported and supposedly refuted over the years. It’s not improbable that some diseases went the other way, but there were probably many more going the other. as Diamond notes in his book, the large quantities and numbers of domesticated animals that the Europeans had (and the Indians, by and large, didn’t) acted as reservoirs for lots of species-hopping diseases.
One question I’ve wondered about is why there wasn’t more disease resistance. We know that the Vikings had contact with the Indians. There’s been much speculation that others may have landed in North America prior to Colummbus – Basque fishermen and others exploiting the Grand Banks seem perfectly plausible. Certainly prior to the arrival of long-term colonists there were explorers and traders. So you’d think there would be exposure to some diseases early on, and with the extensive Indian trading the exposure would have spread. But perhaps the European diseases, when they struck, s so devastatinmg that they wiped out villages whole and prevented the traders themselves from going. Something of that sort seems to have happened in the area of Plymouth, in which the local tribe had been decimated by disease and giving the Pilgrims a dspute-free regioon to settle.

Thanks for the reference, I’ll stop by the library on the way home and that one up.

A newer book that also covers this in detail is 1491 New Revelations of the Americas Before Columbus, by Charles C. Mann which, despite the title, talks mainly about the early contacts between Europeans and Indians.

Diamond sets out the case at greater length and with better citations, but the short answer is domestic animals.

Peoples in the Americas had far fewer domestic animals, (just dogs and llamas and maybe alpacas?) while Eurasians and Africans had cattle, horses, sheep, swine, dogs, chickens, ducks, geese, and probably a couple more. Diseases are capable of jumping hosts (see the current avian flu concern) and with more populations living in contact with more varieties of animals, there is greater chance of such a transpecial jump occurring.

In addition, there is the issue of human-to-human transmission. All of Eurasia and Africa are contiguous by land. An epidemic that originated in any of those regions would tend to sweep across the entire land mass within a couple of hundred years. Every population that was not killed off by the first epidemic would be more resistant to later outbreaks. So measles might have swept across the world in one century, then fall back to being a nuisance disease with periodic outbreaks, then, hundreds of years later, smallpox might sweep across the world and go thorugh the same process, then hundreds of years later some other disease might do the same thing. However, when the Europeans brought their germs to the Americas, they had a reservoir of all the diseases and the Americans had to suffer all the epidemics within a very few short years.

The Viking presence on North America might have simply been free of any of the major epidemic type diseases. (They were not here, that long.)
Even Columbus did not depopulate the entire Caribbean on his first voyage. A reservoir of diseases still need active agents to transport them from one region to a new population. The European invasions subsequent to 1492 were repeated and peresistent.

The Vikings were certainly here long enough to spread disease. They built the settlements at Aux Anse Meadows (and possibly elsewhere), intended to have a presence, ansd brought cattle (which confused and startled the Skraelings). They had all the things needed to bring disease, certainly as much as whoever depopulated the Plymouth area in advance of the Pilgrims. My guess is that any effects they had were localized.

MacNeill’s Plagues and Peoples also offers a good and somewhat more in-depth survey on the topic of the impact of infectious diseases on developing and indigenous populations, and why the peoples of Eurasia were better able to resist infection from without than populations in the Americas were.

As tomndebb and others have pointed out, the proximity of domestic animals in high concentrations due to intensive animal husbandry exposed the populations of Eurasia to many highly active and mutable viruses, whereas there were few large mammals in North America and essentially none kept for food.

Plus, as CalMeacham speculated, a disease that is too virulent won’t retain enough hosts to serve as an effective vector, particularly in an immotile population that does not travel or trade extensively. The relatively innoculous diseases native to the Eurasian continent (chicken pox, various measles, rubella) are caused by the naturally selected decendants of extremely virulent viruses that have evolved to exist in concert with humanity; by becoming less harmful to the host (while at the same time the host becomes better adapted to coping with their mechanisms), they are propagated more freely than their lethal brethren and thus are more fruitful. When exposed to a new, unadapted population, however, they exhibit their atavistic malignity.

It probably doesn’t help that the conquistadors understood the effect their contact–which often included rape and defilement of water supplies–encouraged the spread of disease, even if they were unaware of the specific mechanism behind it. (They probably thought it was God’s Will or somesuch, and used it to justify their attrocious behavior.)


So if it is domesticated animals that was the primary reason for the flood of disease in to the America’s, wouldn’t soon afterwards, these same animals become a reservoir for new world diseases? And if these same animals were returned to Europe (could be ship borne rats or exported cattled/sheep/etc) have the same effect ther as European domesticated animals had in the Americas?

Were the Europeans at that time much more aware of animal disease transmission and better able to stop such outbreak before they occured? Or would the effects been local and outbreaks stopped by human quarantine?

You misunderstand. Many of the diseases that wiped out new wold populations originated in animal population–very crudely, each animal population–cattle, horses, pigs, chickens, geese, dogs–has its own set of diseases. Enough time and contact, and some of those diseases will mutate into forms humans can catch. There weren’t many domestic animals in the New World, so there were fewer possible diseases to pass on to humans, period.

Furthermore, as Tom points out earlier, had the Europeans just brought over one disease, it would have been bad, but nothing like it was–each of those animal diseases mutated to a human-infecting form at a different time. sparing people that already (by random chance) that already had some resistiance to it. Native Americans were only spared if the same individual, by random chance, had resistiance to smallpox AND typhus AND measles AND mumps AND flu. Not nearly as many people like that in a random population.

Correct. The diseases that originated in man had been around long enough that the Native Americans already had them in their population…they crossed the straits from Asia only a few thousand years before people started domesticating animals. The diseases that killed them off were all diseases that originated in animals that humans were in constant close contact with in the Old World.

Just FYI – the jury is evidently still out on whether syphilis came over from the New World or not:

There is still an element of chance involved, however. The settlers of L’Anse Aux Meadows were a small group of people who arrived from the limited populations of Iceland and Greenland. It is not as though everyone of European ancestry was walking around with their own private reservoirs of smallpox, measles, chickenpox, etc., ready to spring it on the local populations at a moment’s notice. If a specific (small) population of Europeans happened to be free of any lethal diseases, the natives would not have been harmed. Columbus did not bring any diseases on his first voyage. In fact, smallpox did not make it across the Atlantic until 1519–seventeen years after that first voyage. On the other hand, a single explorer accompanying De Soto appears to have been responsible for the depopulation of the American Southeast.

Similarly, I have seen no evidence that the Scandinavian cattle provided a disease vector to the European population in the eleventh century (or the late tenth century to get the appropriate lead time to arrive in Newfoundland). It is not a matter of cattle constantly providing new diseases to humans on an ongoing basis. Periodically, a bug will jump from livestock to humans. At that point, it will (frequently) become a plague or epidemic, then die back and mutate into something less lethal. The presence of cattle would have meant nothing unless cowpox happened to pick that very moment to jump to humans.

We are currently concerned about the jump of avian flu, but after multiple outbreaks, Southeast Asia has not (yet) been depopulated (despite serious mismanagement by the Chinese government) and the first human-to-human transmission appears to have only occurred this year.

Something I always wondered: Why didn’t the “quarantine” of a 6-week+ sea voyage render the sailors safe?

Well, to take smallpox:

It has a typical 12-day (range 7 - 17 days) incubation period during which the person is not infectious and shows no symptoms.
It then has a fever stage of roughly two days (very infectious) and a rash stage of just under two weeks during which time it is highly infectious for about six days.

So the sailor goes up town and gets exposed on day 1.
The ship sails some time between day 1 and day 12 with the symptom free sailor aboard.
One to 12 days out on the voyage, the sailor shows symptoms. Rather than simply hurling him into the sea, since most of the sailors know that they are already immune from having caught it earlier or that he and they have some decent chance to survive it–and have probably already been exposed, anyway, his shipmates quarantine him within the ship, but, lacking 19th century knowledge of immunology, probably disperse it around the ship. Not everyone catches it directly from the infected sailor, so the disease now has another two weeks to infect a few more sailors who will pass it on to a few more sailors in another two weeks. By the end of the voyage, everyone has probably been exposed and only the last couple of victims are still infected.
Of course, bedding and such that picked up the virus from spit or sweat may not be claened thoroughly enough, (Louis Pasteur was born too late), so some of those cloths may be passed to people ashore who then contract the disease and start the cycle all over.

Some people will be carriers of a disease even if they themselves aren’t effected by it – like the famous “Typhoid Mary”.

I read something once about how the original smallpox vaccine was brought to the New World. It’s been a while and I don’t have a cite, so forgive me if I don’t get the details exactly right.

In that time, the vaccination was essentially just taking pus from the wound of someone with cowpox and sticking it in the person to be inocculated. They didn’t have any way of storing the live cowpox virus. This presented a problem when they wanted to bring it to the New World, because cowpox doesn’t last very long - a person with cowpox sores when he started the voyage wouldn’t have them by the time he got there.

So what they did was they gathered up a bunch of orphans (I think around 30) and loaded them on the ship, and infected one with cowpox. When his sores started producing pus, they used it to infect the next orphan, and continued the process until they got to the Americas.

I thought that was pretty damn clever and a good use of orphans.

The ones who survived?

Thanks for the clarification.

Aside from really hoping that that story is invented, I would note that smallpox was prevalent on both sides of the Atlantic by the time that the first innoculations were developed and people on the “wrong” side of the Atlantic should have been able to simply visit people who were already infected to acquire the pus. (And how did they keep the innoculant without refrigeration to transport it from, say, Boston to Providence to New York to Philadelphia to Baltimore, to Williamsburg? I have doubts regarding the story.)