When the Europeans travelled to the New World and brought the diseases that wiped out so many Native Americans, why didn’t the local diseases have the same impact on them?

Question

Were the endemic diseases just less severe?

In: Other

Answer 1

There are a lot of theories here, several of which are sound.

Europe, Asia, and Africa simply had a lot more people, so more diseases. The people they did have, generally more cities with more density, and then vast trade networks that spread diseases around. The animals those people raised and interacted with tended to have more diseases that could jump to humans and were more serious (notably from cattle).

To some degree it was dumb luck. There are a bunch of diseases which killed a lot of people in childhood in Europe, but then left you mostly immune until old age or your whole life. The problem is that when those diseases hit populations with no immunity, even into the mid 1800s when governments were really trying to avoid the spread, they would hit a village of people and kill 60-80% of everyone, all the potential caregivers would get sick at the same time as everyone else and then that was it. Those diseases could have been different, or it could have just been bad luck if North American bison or alpacas or something carried some very serious disease for people and it spread to Europe. When we talk about these things, it is mostly odds. More people, in more cities, more trade, more exposure to animals that can carry human diseases (cattle, rats, birds) all increase the chances of those diseases. But it could have gone the other way.