Enterotoxigenic Escherichia coli - Escherichia coli: Pathotypes and Principles of Pathogenesis - page 178

with diarrheal illness, accounting for hundreds of thousands of deaths each year.
Moreover, these illnesses appear to contribute substantially to overall morbidity
and may relate to delayed growth in infected children ( Petri et al., 2008 ).
Traveler's diarrhea
The diarrheal attack rate among travelers is appreciable with roughly one third
to one half ( Merson et al., 1976 ; Sack, 1990 ) of them becoming ill, often within
days of arriving at their destination. Since shortly after ETEC were identified as
a causative agent of diarrheal illness, they have been linked to diarrhea in travel-
ers. In virtually every series ETEC is the predominant pathogen accounting for
more than half of the cases where an etiologic agent is identified ( Black, 1990 ;
Sack, 1990 ). Largely, this is a reflection of the fact that many travelers under
study arrive from regions with adequate sanitation at destinations where sanita-
tion is substandard. Without immunity established by repeated exposure, travel-
ers to developing countries are at high risk for acquisition of ETEC infection as
these organisms are ubiquitously distributed in regions where sanitation is poor
( Subekti et al., 2003 ).
Non-governmental organization (NGO) personnel
military deployment and diarrhea
Soldiers, NGO personnel, and Peace Corp volunteers deployed to regions where
sanitation is often quite poor often fall victim to infectious diarrhea during their
deployment. Data from this subset of travelers provide valuable insight into
the global epidemiology of infectious diarrheal pathogens as these individuals
are often deployed for extended durations to areas not frequented by tourists
where local microbiologic data are otherwise lacking ( Haberberger et al., 1991 ;
Hyams et al., 1991 ; Bourgeois et al., 1993 ). Of the many studies performed in
this population, most have also found ETEC to be the predominant pathogen
( Riddle et al., 2006 ).
Seasonality in developing countries
In Bangladesh, there is considerable seasonal variation in ETEC with biannual
peaks of illness in the warmer spring and early fall periods ( Qadri et al., 2005,
2007 ). Similarly, diarrheal illness in Egypt has been shown to peak in warmer
months of the year ( Abu-Elyazeed et al., 1999 ), and in studies of travelers with
diarrhea in Mexico, the rate of ETEC infections increased by 7% for every
degree centigrade increase in ambient temperature ( Paredes-Paredes et al.,
2011 ).
Emergence of ETEC in developed countries
Interestingly, despite the clear preponderance of ETEC infections in devel-
oping regions of the world, a spate of large-scale ETEC outbreaks in the US
( Rosenberg et al., 1977 ; CDC, 1994 ; Dalton et al., 1999 ; Beatty et al., 2004 ;