travelers' diarrhea usually is contracted by the ingestion of contaminated food or water. contrary to common belief food -- not water -- is primarily at fault. most cases of travelers' diarrhea are caused by bacteria. the most important bacterium is enterotoxigenic e. coli which is estimated to account for up to 70% of all cases. most e. coli are harmless. however there are five unique classes of e. coli that can cause inflammation of the stomach and bowels (gastroenteritis) and are termed enterovirulent. they are virulent (extremely noxious) for the intestine (or in greek the enteron). collectively these five classes of enterovirulent e. coli are referred to as the eec group (enterovirulent e. coli). each class of eec is distinct and different from the others. enteroinvasive e. coli (eiec) invades (passes into) the intestinal wall to produce severe diarrhea. enterohemorrhagic e. coli (ehec): a type of ehec e. coli 0157:h7 can cause bloody diarrhea and the hemolytic uremic syndrome (anemia and kidney failure). enterotoxigenic e. coli (etec) the one that causes most of travelers' diarrhea produces a toxin that acts on the intestinal lining. enteropathogenic e. coli (epec) can causes diarrhea outbreaks in newborn nurseries. enteroaggregative e. coli (eaggec) can cause acute and chronic (long lasting) diarrhea in children. other bacterial species implicated in travelers' diarrhea include campylobacter jejuni shigella and salmonella. viruses (including rotavirus norwalk virus and other enteric viruses) less commonly are causes of travelers' diarrhea. parasitic infections are an uncommon cause with the exception of giardia lamblia which should be suspected in individuals traveling to russia or to mountainous regions of the northern hemisphere. cryptosporidia another parasite also has been implicated as a common cause of diarrhea in visitors to st. petersburg russia.
what causes travelers' diarrhea?