Travelers' diarrhea: update on the incidence, etiology and risk in military and similar populations - 1990-2005 versus 2005-2015, does a decade make a difference?

Abstract

Background: Travelers' diarrhea remains a prevalent illness impacting individuals visiting developing countries, however most studies have focused on this disease in the context of short term travel. This study aims to determine the regional estimates of travelers' diarrhea incidence, pathogen-specific prevalence, and describe the morbidity associated with diarrheal disease among deployed military personnel and similar long term travelers.

Methods: We updated a prior systematic review to include publications between January 1990 and June 2015. Point estimates and confidence intervals of travelers' diarrhea and pathogen prevalence were combined in a random effects model and assessed for heterogeneity. Eighty-two studies were included in the analysis, including 29 new studies since the prior systematic review.

Results: Military personnel were evaluated in 69% of studies and non-military long term travelers in 34%, with a median duration of travel of 4.9 months, and travel predominantly to the Middle East, Southeast Asia, and Latin America and the Caribbean. Sixty-two percent of tested cases were due to bacterial pathogens, with enterotoxigenic E. coli (ETEC), enteroaggregative E. coli (EAEC), and Campylobacter predominating, and significant regional variability. The incidence of TD from studies with longitudinal data was 36.3 cases per 100 person-months, with the highest rates in Southeast Asia, Latin America and the Caribbean, and the Middle East, with higher estimates from those studies using self-reporting of disease. Morbidity remained significant, with 21% being incapacitated or placed sick in quarters (SIQ) by their illness, 15% requiring intravenous fluids, and 3% requiring hospitalization.

Conclusions: In comparison to results from the prior systematic review, there were no significant differences in incidence, pathogen prevalence, or morbidity; however there was a trend toward improved care-seeking by sick individuals.

Keywords: Campylobacter; Enteroaggregative E. coli (EAEC); Enterotoxigenic E. coli (ETEC); Long term traveler; Travelers’ diarrhea.

Fig. 1

Flow diagram of study selection for inclusion in the updated systematic review. We identified 454 candidate studies for inclusion since the last systematic review by query of electronic bibliographic databases. After review of titles and abstracts, 193 studies were identified for full review, with 164 studies excluded. Thirty studies were identified for inclusion in the final systematic review, with a total of 82 studies when those from the prior review were included

Fig. 2

Pathogen prevalence of diarrheal illness among long term travelers, 1990–2015. Of those cases for which diagnostic testing was performed, 62% were positive for bacterial pathogens, with viruses (7%) and parasites (4%) being detected at lower rates. ETEC was the most commonly isolated bacterial etiology (44%), followed by EAEC (21%) and Campylobacter spp. (19%). Multiple pathogens were detected in 11% of tested cases and no identified pathogens in 36%

Fig. 3

Region specific pathogen prevalence of diarrheal illness among long term travelers, 1990–2015. We identified variability of pathogen prevalence across studies from different regions. In Latin America/Caribbean, Africa, and the Middle East, the most common identified pathogen was ETEC, while in SE Asia Campylobacter spp. predominated

Fig. 4

Incidence of diarrheal illness among long-term travelers, 1990–2016. We found an estimated overall pooled incidence of TD among long-term travelers of 36.3 cases per 100 person-months. Studies included in the prior systematic review (AJTMH, 64(5), 2006) are listed at the top of the forest plot, with studies since that time included at the bottom of the figure (2018 Update). Weights calculated by random effects model