Seasonality of Diarrheagenic Escherichia coli Pathotypes in the US Students Acquiring Diarrhea in Mexico

The frequency of Travelers’ diarrhea (TD) among international travelers to tropical and semitropical regions of the developing world ranges from 10% to 60%. The highest rates of TD are seen in Latin America, Africa and the Indian subcontinent [1]. Worldwide infectious diarrhea rates are influenced by seasonal changes. Striking examples include V. cholerae infection in Asia where the rates of infection double during the warm season [2]. In Mexican children, rates of diarrhea are also influenced by seasonal changes with rotavirus diarrhea predominating in winter months [3]. In the US, pediatric diarrhea rates also vary seasonally, with viral causes of diarrhea predominating during the winter months and enteroaggregative E. coli (EAEC) seen more commonly during spring time [4]. The microbiology of TD in US visitors to Mexico reflects the bacterial enteropathogens identified in Mexican children with diarrhea. Most TD acquired in Mexico is due to enterotoxigenic Escherichia coli (ETEC) and EAEC [5, 6]. Previous studies have shown that the TD overall and TD due to ETEC are more common during summer than during winter months [7–9]. In other regions of the world, investigators have also found seasonal variation in etiology of TD; for instance in a study conducted in Morocco, Campylobacter spp. was associated with TD during winter months and ETEC was seen more commonly identified during the fall months. This is felt to relate to an increase in the ambient temperature and rainfall favoring the growth and spread of bacteria that contaminate food and water. These changes may further evolve in response to current global climate changes. The aim of this study was to characterize seasonal differences in diarrheagenic Escherichia coli pathotypes as causes for TD over a thirteen month period in a popular tourist destination in Mexico.