Dysentery has almost disappeared in the Western world. Yet prior to the decline in infectious diseases among causes of death in the 1800s, dysentery was a major killer.
You can read more about the study in Sweden in the ScienceDaily web site at http://goo.gl/5B8OQ. While this study focused only on Sweden, similar problems existed throughout Europe and North America.
My thanks to newsletter reader Paul Roberts for telling me about this article.