Can immunity to diseases vary by populations?

Question

A common explanation for the massive population decreases of isolated societies upon contact with Europeans during the Age of Discovery is that the natives lacked immunity to newly introduced diseases. What does this actually mean? Is it just a shorthand for "the adult population was not subjected to these pathogenes during childhood and is therefore more susceptible to them" or is there maybe a certain genetic component to it?

Answer 1

Your first phrase is correct. For the individuals of a population to have immunity against a disease, the microbial agent of the disease has to be introduced to the individuals. In the example of the natives, they had not been introduced to the microbes of the Europeans. Therefore, they were not immune. For this reason, when the natives contracted their diseases, they experienced high death rates.

As for genetics, it plays some part in developing immunity. (Feel free to use google to find these.) The majority of the time immunity relies upon being exposed to the pathogen or, as in vaccines, a weakened form of the pathogen, to develop immunity.