The American Experience program ascribes the deaths among the local indigenous groups to "the plague." That term is really just a placeholder for one or more diseases to which the local population had no immunity and therefore suffered badly. One of the references on the program's website is to a paper published in Emerging Infectious Diseases in 2010 by John May and John Cathey.
In the years before English settlers established the Plymouth colony (1616–1619), most Native Americans living on the southeastern coast of present-day Massachusetts died from a mysterious disease. Classic explanations have included yellow fever, smallpox, and plague. Chickenpox and trichinosis are among more recent proposals. We suggest an additional candidate: leptospirosis complicated by Weil syndrome. Rodent reservoirs from European ships infected indigenous reservoirs and contaminated land and fresh water. Local ecology and high-risk quotidian practices of the native population favored exposure and were not shared by Europeans. Reduction of the population may have been incremental, episodic, and continuous; local customs continuously exposed this population to hyperendemic leptospiral infection over months or years, and only a fraction survived. Previous proposals do not adequately account for signature signs (epistaxis, jaundice) and do not consider customs that may have been instrumental to the near annihilation of Native Americans, which facilitated successful colonization of the Massachusetts Bay area.We will probably never know for sure exactly what wiped them out, but it is interesting to contemplate how different the world of today might be if the indigenous population had been resistant to these diseases. The ability to have casinos seems small compensation, albeit more than has been offered to American blacks, as Larry Wilmore points out in the title of his new book.