How To Hit the Runs for Fifty Million Travelers at Risk

DuPont and colleagues' article in this issue on travelers' diarrhea among North American students in Mexico (1) reminds me that I have just passed the 50th anniversary of my first Mexican trip, where I experienced the joys of travel and its accompanying intestinal agonies. It is remarkable how little progress we have made in controlling this illness over the past half century. Among the approximately 50 million persons who travel each year from industrialized countries to resource-constrained countries, the incidence of diarrhea ranges from 30% to 50%. This incidence has remained stubbornly fixed at this level in many areas of Latin America, Africa, and Southern Asia. We learned 30 years ago that enterotoxigenic Escherichia coli is the major pathogen of travelers' diarrhea (2), certainly in Mexico, but it accounts for fewer than half of the cases. Even using advanced microbiological methods, we have failed to identify a known pathogen in many of the remaining cases. We have studied prophylaxis of travelers' diarrhea with antimicrobial drugs since 1959 (3). Scores of subsequent studies have shown that such drugs as doxycycline, trimethoprim–sulfamethoxazole, and fluoroquinolones are effective. Protection has ranged from 72%, as in DuPont and colleagues' study of rifaximin, to more than 90% with fluoroquinolones. Like climbing mountains, even if prophylaxis is possible, it is still not clear that this approach is appropriate for all travelers at risk.

The effectiveness of antimicrobial prophylaxis …