I was in Mexico in the summer of 2013 when I came down with a bad case of diarrhea. That’s a pretty common complaint among travelers, so I figured it was just an intestinal bug. The problem continued off and on for several weeks, even after I returned to the States. I tried to ignore it and just get on with my life, but I’m a middle school teacher, and summer is my break time. I had training and traveling to do.

Then I started...