A significant increase in the number of international travelers has been observed during previous decades globally. The length, diversity and complexity of travel itineraries and activities also have been increased. Moreover, travelers often visit remote tourist destinations where the available healthcare services are inadequate. Unfortunately, this international trend has been associated with more travel-related health problems and instances of diseases that are imported to the country of origin.
Waterborne and foodborne diseases are considered as main travel-related health problems. These diseases include travelers’ diarrhea, hepatitis A, hepatitis E, typhoid fever, and cholera. Ingestion of fecally contaminated food and water is considered as the primary travel-related mechanism of these infections. In areas where large part of the population has no access to water and sanitation systems, the increased amount of environmental stool contamination is accessible to insects, like flies. Moreover, washing foods in contaminated water can lead to a direct contamination. Unsafe food storage is another problem that is frequently observed in regions with inadequate electrical capacity resulting in poorly functioning refrigeration. In restaurants, inadequate water supplies and poor training of the staff are associated with inadequate hand-washing and poor disinfection of food preparation surfaces and utensils, as well as cases of cross-contamination from meat during handling and preparation of food.
Travelers' diarrhea (TD) is the most common disorder affecting international travelers. The rates of TD are in the order of 40%–60% over a 2–3-w vacation for travelers from industrialized countries traveling to developing regions. The most important risk factor is the traveler's destination. Low-risk parts of the world include North America, Australia, New Zealand, Japan, and countries in Northern and Western Europe. Intermediate-risk areas include countries in Eastern Europe, South Africa, and some of the Caribbean islands. High-risk regions include most of Asia, the Middle East, Africa, and Central and South America. Individuals at particular high-risk include young adults, immunosuppressed patients, and travelers with inflammatory bowel disease or diabetes mellitus. Administration of H-2 blockers or antacids seems to increase the risk. Another important factor is the season of travel. The clinical syndrome can result from a variety of intestinal pathogens. Approximately 80% of cases are linked to bacterial enteropathogens, mainly enterotoxigenic Escherichia coli (ETEC), enteroadherent and other E. coli species. Other bacterial causative agents include Campylobacter jejuni, Shigella spp., and Salmonella spp. Intestinal viruses, including norovirus, rotavirus, and astrovirus, account for about 5%-8% of TD cases. Besides bacterial and viral causative agents, protozoal pathogens are linked to approximately 10% of diagnoses, particularly in long-term travelers. Giardia is the main protozoal pathogen and the risk for Cyclospora is highly seasonal and geographic (Guatemala, Peru, Haiti, and Nepal). Dientamoeba fragilis is occasionally found in travelers. TD is rarely a life-threatening syndrome. Approximately 90% of cases resolve within 1 w, and 98% resolve within 1 m. However, about 25% of patients will have to change their planned activities, and some will be left with a post-infectious irritable bowel syndrome. The ingestion of preformed toxins in food (food poisoning) is associated with vomiting and diarrhea, but symptoms usually resolve spontaneously within 12 h.
Hepatitis A is the most common vaccine preventable infection of international travelers (approximately 2,000 cases per 1,000,000 non-immune travelers per month). Moderate- to high-risk regions for hepatitis A include all parts of the world except Western Europe, North America, Japan, Australia, and New Zealand. Hepatitis A virus (HAV) is shed in the stool. Fecal-oral routes are considered as the main mode of spread, including contaminated food and water, and person-to-person contact. The risk is higher for campers and hikers, but there is also significant risk for those who visit only urban areas or stay at luxury hotels. Acute hepatitis caused by hepatitis A virus (HAV) may be a severe, even life-threatening infection. Clinical manifestations include fever, malaise, myalgia, and anorexia, followed by jaundice in approximately 80% of adults. Sporadic and epidemic acute hepatitis caused by the enterically transmitted hepatitis E virus (HEV) has been reported especially in developing countries.
Typhoid fever is an infection caused by the bacterium Salmonella typhi that is spread by water and food contaminated with feces of chronic carriers or acutely ill patients. Clinical manifestations include fever, headache, anorexia, myalgia, and malaise. Meningitis, heart valve infections, bone infections, and septic shock are severe complications of this infection which is life-threatening if left untreated. Endemic areas of typhoid fever include Africa, Central and South America, the Middle East, Southeastern Asia, China, and other parts of the world. Cholera is caused by the bacterium Vibrio cholerae which is spread by the ingestion of contaminated water and food. Occasional outbreaks among travelers have been reported, mainly associated with contaminated seafood. Endemic areas include countries in Africa, Asia, and other parts of the world. The syndrome can be fatal for patients particularly prone to severe dehydration, such as small children.
Travel medicine deals with the prevention and management of international travelers. The ﬁeld has evolved as a distinct discipline over the last three decades. It is represented by an international society, the International Society of Travel Medicine (ISTM). Currently, an increasing number of travel clinics provide travel health services in various countries. Pre-travel visit includes a health risk assessment of the trip based on the underlying health status of the traveler (age, health conditions, medications, immunization history) and the details of the trip (season of travel, itinerary, duration, planned activities). Moreover, pretravel visit should be used to update vaccinations that are routinely recommended. Vaccination against hepatitis A may be indicated.
Advice regarding waterborne and foodborne diseases represents a very important component of the pre-travel consultation, especially for individuals planning to travel to resource-poor areas. Preventive measures can reduce, but never completely eliminate, the risk of these disorders. According to the Centers for Disease Control (CDC) recommendations, travelers should avoid eating raw or undercooked meat and seafood, and raw fruits and vegetables unless the traveler peels them. Furthermore, travelers should seek restaurants and other locations of food consumption that have an excellent reputation for safety. If handled properly, well-cooked and packaged foods are safe. On the other hand, tap water, ice, unpasteurized milk, and dairy products are associated with increased risk for waterborne and foodborne infections. Safe beverages include bottled carbonated beverages, hot tea or coffee, beer, wine, and water boiled or appropriately treated with iodine or chlorine. Although compliance with the instructions regarding food and beverage selection is extremely important, educating travelers about safe beverage and food choices has often failed to lead to behavioral changes since sampling the local cuisine is an integral part of the enjoyment of travel.
Public Health Interventions
Previous studies suggest that inadequate public health practices in locations of food and beverage consumption might be a more important risk than contamination of speciﬁc food and beverage items. The World Health Organization (WHO), CDC, European Center for Disease Prevention and Control (ECDC), several Ministries of Health, and other public and private organizations are working to improve food and water safety around the world. Studies investigating risk factors associated with waterborne and foodborne infections assist in identifying more effective preventive measures. In addition, public health organizations, frequently in collaboration with international agencies, are working to improve sanitary conditions in accommodations worldwide and consult the local authorities with travel medicine specialists.
Many public and private organizations, universities, and institutions offer valuable information regarding foodborne and waterborne diseases through the Internet:
- WHO: Travel and health (http://www.who.int/topics/travel/en/).
- CDC: Travelers’ health (http://wwwnc.cdc.gov/travel/page/food-water-safety).
Moreover, mobile application ‘2014 Yellow Book’ covers travel health issues and mobile application ‘Can I eat this?’ focuses on travelers’ diarrhea (http://wwwnc.cdc.gov/travel/page/apps-about).