Food and Water Safety: Geographic Variations
Abstract & Commentary
By Philip R. Fischer, MD, DTM&H
Dr. Fischer is Professor of Pediatrics, Division of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
Dr. Fischer reports no financial relationship related to this field of study.
Synopsis: Bacterial contamination of food and drinking water are global problems. Travelers should always exercise caution even though problems are less often noted in more developed regions of the world.
Source: Beatty ME, et al. Epidemic Diarrhea Due to Enterotoxigenic Escherichia coli. Clin Infect Dis. 2006;42:329-334.
In June 1998, there were numerous reports of diarrheal illness in multiple attendees of events catered by a delicatessen in Chicago, Illinois. An investigation revealed that more than 16,000 individuals had attended many events catered by this delicatessen during a 3-day period. An epidemiological study was done on 612 attendees of 11 of these events. Approximately 20% of attendees developed acute gastroenteritis, but none were hospitalized, and no deaths were reported. Ingestion of several different food items (potato salad, macaroni salad, egg salad, and watermelon) was associated with illness. Stool and serologic testing implicated Escherichia coli O6:H16 in the epidemic, and this organism was found to produce both heat-stable and heat-labile toxins. (This organism is distinct from the O157:H7 strain that is commonly associated with beef products.)
No food handler admitted to having had recent illness, a history of recent foreign travel, or recent contact with foreign visitors. However, the food production of the delicatessen was about twice as great as usual during the week of the epidemic illness. (As an example, 2889 kg of potato salad were produced during the week and then stored in 22.5 kg containers. Due to limited refrigerator space, some salad was stored in a refrigerated truck without reliable temperature controls, and salads were delivered to some events without refrigeration.) Salad ingredient preparation and mixing was done manually. There were neither soap nor paper towels in the main kitchen. A new dishwasher had been installed in the delicatessen just prior to the beginning of the epidemic; during that time, there were areas where low-pressure water could stagnate and potentially mix with waste water. Serologic testing of delicatessen workers was performed 2 weeks after the initial cases of illness. By the time of the investigation, however, no enterotoxigenic Escherichia coli were found in either food handlers or in the delicatessen.
Thus, an epidemic of gastroenteritis due to enterotoxigenic Escherichia coli (ETEC) affected approximately 3300 people in Chicago in June 1998. The epidemic was linked to poorly stored food and potential mixing of wastewater with the potable water system in a single delicatessen.
Practitioners of travel medicine are well aware of the risk of ETEC gastroenteritis in travelers who ingest improperly prepared foods or beverages in developing countries. The paper from Beatty and colleagues at the CDC and at county and state public health agencies in Illinois serves to remind us, however, that ETEC diarrhea is not limited to locations outside of North America. Traveler’s diarrhea is simply not limited just to travelers.
Much of travel medicine deals with balancing the risks and benefits of preventive interventions. Usually, it is not necessary to avoid salads at catered events in the United States, and previously cooked, stored foods may be eaten without worry. This paper, however, illustrates that any lapse in attention to food and water hygiene can prove disastrous.
Where in the world is water usually safe? The Cryptosporidium outbreak in Milwaukee in the early 1990s showed that even expensive, elaborate municipal water treatment systems can become contaminated.1 Up to about half of travelers to developing countries develop diarrhea,2,3 but the incidence of illness is greater in less developed countries. Unfortunately, most travelers do not follow routine food and water hygiene recommendations.4 Interestingly, though, there is some evidence that implementation of food and water recommendations do not correlate with prevention of diarrhea.5
While traveler’s diarrhea rates vary geographically,6 there is no accurate way to predict an individual traveler’s risk of bacterial contamination within and between foreign destinations. Anecdotal evidence from a 7th grade science project, however, provides a basis for some observations that could potentially be validated in a more rigorous study.
Joanna Fischer obtained water samples from several countries from her globe-trotting father as part of a science project at Schaeffer Academy in Rochester, Minnesota. Water samples were plated on blood agar, and the presence or absence of subsequent bacterial growth was noted. Table 1 shows her results.
Water available for drinking in industrialized nations (Japan, United Kingdom, United States) seems relatively safer than water in less industrialized countries. One of the British samples came from a tap on a train that was labeled "not for drinking;" travelers should know that minerals and toxins can pose problems even when water is not contaminated with bacteria. Second, water from resorts and conference centers (such as the ones tested in Mexico and Kenya) with private treatment facilities likely poses less risk to travelers than does water obtained from taps throughout surrounding municipal areas. Third, even in seeming modern areas of developing countries such as Thailand, food and water precautions are still likely indicated. Indeed, a recent review of illness in returned travelers highlighted the frequency of traveler’s diarrhea in individuals returned from Asia.6
Travel medicine specialists are concerned with the health of residents of developing countries.7 In the developing world, resources should be allocated to improve the safety of locally available drinking water. And, even in seemingly developed nations, residents and visitors should remain vigilant to ensure that appropriate food and water hygiene measures are implemented. Until then, the future development of an effective and affordable ETEC vaccine offers additional hope of protection.8
- Eisenberg JN, et al. The Role of Disease Transmission and Conferred Immunity in Outbreaks: Analysis of the 1993 Cryptosporidium Outbreak in Milwaukee, Wisconsin. Am J Epidemiol. 2005;161:62-72.
- Pitzinger B, et al. Incidence and Clinical Features of Traveler’s Diarrhea in Infants and Children. Pediatr Infect Dis J. 1991;10:719-723.
- Steffen R, et al. Epidemiology of Travelers’ Diarrhea: Details of a Global Survey. J Travel Med. 2004;11:231-237.
- Rack J, et al. Risk and Spectrum of Diseases in Travelers to Popular Tourist Destinations. J Travel Med. 2005;12:248-253.
- Hillel O, Potasman I. Correlation Between Adherence to Precautions Issued By the WHO and Diarrhea Among Long-Term Travelers to India. J Travel Med. 2005;12:243-247.
- Freedman DO, et al. Spectrum of Disease and Relation to Place of Exposure Among Ill Returned Travelers. N Engl J Med. 2006;354:119-130.
- "The Responsible Traveler" at www.istm.org, accessed 2-17-06.
- Daniels NA. Enterotoxigenic Escherichia coli: Traveler’s Diarrhea Comes Home. Clin Infect Dis. 2006;42:335-336.