The quick and dirty answer is that Europeans did often fall ill in the New World, and in many cases we assume these deaths were from diseases they encountered in the Americas. As I dive into this question, though, I will address a few myths about the nature of disease after contact, and hopefully detail the complexity of disease transfer after contact.
First, and contrary to popular opinion, the New World was not a disease-free paradise. About a year ago I wrote a post about evidence for epidemic diseases in the New World before contact. In that post I mentioned New World populations played host to a wide variety of intestinal parasites (roundworm, hookworm, whipworm, etc.), gastrointestinal diseases (Giardia, Entamoeba, and Cryptosporidium, etc.), Chagas disease, syphilis, Rocky Mountain Spotted Fever (and possibly Lyme), and tuberculosis. I also hypothesized they would be subject to occasional zoonotic events (when a non-human pathogen jumps into human hosts), just like modern populations with frequent access to wildlife/bushmeat trade. There is also reason to believe that observed epidemics that occurred after contact, like the cocoliztli (a Hanta Virus-like hemorrhagic fever) epidemics that swept through Mexico in the sixteenth century, were present, though perhaps more contained, before contact. Two cocoliztli epidemics, in 1545 and 1576, killed between 7 and 17 million people in highland Mexico. There is no evidence the pathogen responsible for the epidemic arrived from the Old World, but researchers suspect a massive drought altered the relationship between the murine host and humans, leading to increased chance of pathogen transmission, and a catastrophic epidemic.
Next, when we read the accounts of early Spanish entradas in the U.S. Southeast, the authors make specific mention of crew members becoming ill weeks after their arrival in new lands. Nutritional and physiological stress from poorly planned colonization attempts likely decreased their immune defense, leaving them vulnerable to illness. Ayllón's 1526 attempt to establish a settlement on the Santee River in South Carolina ended in disaster. Of the original 600 colonists, all but 150 died from exposure, famine, and disease. Later, the 1528 Narváez entrada likewise suffered a series of unfortunate events in their attempts to find riches in Florida. 400 men landed in Tampa Bay, yet only four survived the trip to Florida. After a month of raiding Apalachee towns, members of the entrada began to fall ill. Cabeza de Vaca says
there were not horses enough to carry the sick, who went on increasing in numbers day by day... the people were unable to move forward, the greater part being ill.
Did members of Ayllón and Narváez's entrada perish from New World pathogens, or did they bring their own microbes with them, and perish as a result? We don't know for sure. The deaths began outside the incubation period for many common pathogens, giving us reason to suspect they did not bring those illnesses with them from Cuba, but rather encountered them from the neighboring maize-based agricultural populations like the Apalachee.
Continued below...
Well, actually, Europeans did get quite sick from New World diseases...one need look no further than syphilis (there are others, I'm sure...but syphilis is kinda a big deal).
Within recent years, new evidence has strongly indicated that syphilis got a ride back with some of the first European explorers to the Americas. More here And...even more
The sexual exploitation of the native population by Christopher Columbus & his crew is well documented, and so one can assume that this nasty bug was on some of the first ships back from the New World in the late 1400s.
Since first appearing in the early 16th Century, syphilis blighted Europe for centuries until penicillin came along. Its sudden spread and virulent nature was compounded by the rich social meaning that it came to bear--on top of that, its association with the sexual made it all the more potent as a cultural sign of sex gone bad. Initially, syphilis was called the "French disease" by Italians and the "Italian disease" by the French (you see what they did there?). It's mysterious and sudden arrival was almost as terrifying as the Plague. As Claude Quetel detailed in the History of Syphilis, syphilis, with it's sneaky stages and symptoms, soon began emerging in art, poetry, and literature. For example, the tell-tale black blotches on the faces of louches in William Hogarth's paintings indicated that syphilis had caught up with the bad habits of the rich. Syphilis was also a shameful mark of innocent victims--husbands who brought syphilis back to their wives, who then bore children with congenital syphilis, who gradually manifested the grotesque facial disfiguration of tertiary syphilis as the years went by.
Lots of scholarly work explores how syphilis transformed the sexual and social landscape. Here are just a few: Lit review on syphilis Shakespeare and syphilis Hairpin article The Guardian
