Routes of Infection: Travel and Risk

SPECIAL COVERAGE

By Mary E. Wilson, MD

Travel makes people worry. the imagination runs wild with scenarios—rare tropical diseases, attacks by unearthly insects, ridicule and arrest for misunderstanding some simple request. Everyone has heard stories and remembers the most bizarre and embellished.

Travelers are often concerned about exotic diseases and rare risks. Perhaps this heightens the sense of adventure about the trip. The unknown provokes greater anxiety than daily, familiar activities that may, in actuality, be much riskier. Despite their grip on the public imagination, Ebola in Africa and tuberculosis on airplanes are not the biggest threats to travelers today.

This discussion outlines 10 risks that should be on the minds of physicians and travelers. Physicians counseling prospective travelers and caring for sick persons after their return should have a general awareness of the relative risks of threats to travelers. Although this list was prepared with the infectious diseases physician in mind, it is also pertinent to other physicians.

1. The most common infectious diseases after exotic travel are not exotic infections but, rather, infections with a worldwide distribution. The risk of acquiring many infections with a worldwide distribution, such as hepatitis A, typhoid fever, shigellosis, campylobacteriosis, and salmonellosis, is much higher in developing countries than in industrialized countries.1,2 This statement, however, must be followed by the emphatic reminder to always check for malaria in anyone with fever or a history of fever after travel to malarious areas. Malaria remains the most important infection to identify promptly, as falciparum malaria can be rapidly fatal in nonimmune individuals.

2. The most common cause of death during tropical travel is not infection. It is not even close. If one excludes underlying diseases, such as cardiovascular disease and cancer, overwhelmingly the most common cause of death during travel is injury.3 The majority of deaths in young travelers are motor vehicle crashes, drownings, aircraft crashes, homicides, and burns. For most destinations, injuries are the most common cause of death and the most common reason for air medical evacuation.4 Each year, an estimated 750 Americans die as a result of injury on foreign roads, and at least 25,000 are injured.5 An organization called the Association for Safe International Road Travel (ASIRT) has tried to compile data on the number of injuries or deaths per 100 million kilometers traveled by country. In some countries, rates of road fatalities are 10- to 40-fold higher than in the United States. Education and behavioral changes can reduce the risk. For example, travelers should be advised to request cars with seat belts, to avoid alcohol when driving, to avoid travel at night and when fatigued, especially when driving on unfamiliar roads, and to seek good maps and instructions before exploring new territories.

3. Sex with new partners is common during travel.6,7 Sexual tourism may be the primary reason for travel. Among short-term Swiss tourists traveling to tropical Africa, Asia, and Latin America, almost 60% of those identified in a high-risk group reported casual sexual contacts during their trip.8 Published studies show disappointingly low rates of use of condoms in several populations of travelers studied. Sexually transmitted pathogens can cause systemic infections that may manifest as undifferentiated fever—acute infection with human immunodeficiency virus (HIV), hepatitis B, cytomegalovirus, or syphilis. Inquire about sexual exposures when evaluating persons with fever and other symptoms after travel.

4. Infections can be acquired en route as well as at the final destination. Food and waterborne outbreaks of infection are common on cruise ships.9 Contaminated food served on airplanes has been a source of outbreaks, including cholera, shigellosis,10 and staphylococcal food poisoning. Food and ice served on aircraft and ships generally come from the port of departure and may reflect conditions in that country. The close quarters on ships and shared, recirculated air on airplanes have allowed spread of infection from one passenger to others, causing several well-documented outbreaks, including influenza,11 enteroviruses, and tuberculosis.12 Cases of Legionnaires’ disease were traced to exposures on a cruise ship.13 When evaluating an ill person posttravel, consider the entire trip, not just the destination.

5. Everyone has heard about (or has suffered from) traveler’s diarrhea, but respiratory tract infections are also common during and after travel.1,2 Despite anecdotal reports, careful studies that evaluate incidence and confirm specific etiology are lacking. Sporadic cases and clusters of Legionnaires’ disease have been related to stays in resort hotels in many parts of the world, including the Caribbean and Europe.2 But Legionnaires’ disease does not account for most travel-associated respiratory infections. Plausible reasons for increased rates of respiratory infections related to travel include prolonged exposure to low humidity in aircraft; exposure to large numbers of persons from many geographic regions, often in crowded places or closed environments such as airplanes, airport terminals, train stations, and busses; and high levels of air pollution in many parts of the world (burning of fossil fuel, high rates of cigarette smoking).

If a traveler is a candidate for pneumococcal vaccine or influenza vaccine, give it before travel. Infection during travel is at a minimum disruptive and unpleasant and can be at worst serious, requiring medical care or hospitalization, which can range from difficult to dangerous.

6. "Hidden" water, or water consumed other than as a glass of water, can be a source of enteric pathogens. Most people are aware of the recommendation to drink only bottled water in developing countries. Contaminated water can also be ingested during showering and brushing teeth (if the person drinks water while performing these activities) and drinking beverages cooked with ice made from contaminated water.14 Alcohol in beverages does not kill the pathogens. What appears to be orange juice or other fruit juice may have been diluted with tap water. Watermelons are sometimes injected with water (of uncertain source) to increase their weight and, thus, their market value.

Recreational water can be a source of gastrointestinal, eye, respiratory, and skin infections. Sewage outlets near beaches may contaminate swimming areas;15 recreational water in many areas is not regularly tested or treated (swimming pools). In parts of Africa, Latin America, and Asia, fresh water can contain cercariae that cause schistosomiasis. Leptospirosis is common in many warm, humid countries. Water contaminated with animal urine is one source of infection.

7. Unfamiliar (and unexpected) infections can follow travel to temperate, developed regions of the world. In the United States, for example, Colorado tick fever, relapsing fever, babesiosis, ehrlichiosis, plague, tularemia, Lyme disease, Rocky Mountain spotted fever, and coccidioidomycosis are among the infections that can be picked up in some regions, often by hikers and persons engaged in vacation activities. Lyme disease is common in many parts of Europe. Rickettsial infections (spotted fever due to Rickettsia conorii) and visceral leishmaniasis are endemic in parts of southern Europe.

8. Immobility induced by long travel, especially by persons crammed into the tight quarters of coach travel (economy class syndrome), has been associated with venous thrombosis and pulmonary emboli.16 Remember to consider this diagnosis in the differential diagnosis of the person with shortness of breath and pleuritic pain after travel.

9. Changes in air pressure that occur with ascent and descent during air travel can precipitate sinus symptoms and lead to exacerbation of chronic sinus problems (or convert minimally symptomatic into acute sinusitis). Travel during acute respiratory infections is a risk factor. Use of decongestants, especially before descent, may prevent acute discomfort.

10. The person’s normal medical insurance plan may provide no coverage for medical care outside the United States. Review of coverage is especially important for persons planning extended travel, for older persons, and for those with underlying medical problems who may need medical attention while abroad. Many companies sell short-term coverage, specifically for the traveler. Persons planning long trips may want to obtain names of physicians in the destination countries. One source of names is the International Association for Medical Assistance to Travelers (40 Regal Road, Guelph, Ontario, N1K 1B5, Tel: 519-836-0102; Fax: 519-836-3412), which also has other materials helpful to travelers.

It is impossible to eliminate all risks associated with travel, but some risks can be reduced through education, specific interventions, and careful preparation. Infectious diseases physicians often are asked to see persons after travel to assess for the presence of one or another exotic diseases. Infectious diseases physicians need to have a good working knowledge of the range of diseases associated with travel and their relative risks. (This article was reprinted with permission from: Wilson ME. Routes of infection: Travel and risk. Infect Dis Clin Prac 1997;6(1):33-35.)

References

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2. Wilson ME. A world guide to infections: Diseases, distribution, diagnosis. New York: Oxford; 1991.

3. Guptill KS, Hargarten SW, Baker TD. American travel deaths in Mexico. Causes and prevention strategies. West J Med 1991;154:169-171.

4. Hargarten SW. Injury prevention: A crucial aspect of travel medicine. J Travel Med 1994;1:48-50.

5. Wilkinson S. Hazardous highways. Guide to the world’s riskiest roads. Conde Nast Traveler 1996;April: 42-48.

6. DeSchryver A, Meheus A. International travel and sexually transmitted diseases. World Health Stat Q 1989;42:90-99.

7. Mulhall BP. Sexually transmissible diseases and travel. Br Med Bull 1993;49:394-411.

8. Stricker M, Steffen R, Cutzwiller F, et al. Casual sexual contacts of Swiss tourist in tropical Africa, the Far East, and Latin America. In: Lobel HO, Steffen R, Kozarsky PE, eds. Travel Medicine 2. Atlanta: International Society of Travel Medicine; 1992;220:1.

9. Koo D, Maloney K, Tauxe R. Epidemiology of diarrheal disease outbreaks on cruise ships. 1986 through 1993. JAMA 1995;275:545-547.

10. Hedberg CW, Levine WC, White KE, et al. An international foodborne outbreak of shigellosis associated with a commercial airline. JAMA 1992;260:3208-3212.

11. Moser MR, Bender TR, Margolis HS, et al. An outbreak of influenza aboard a commercial airliner. Am J Epidemiol 1979;110:1101-1106.

12. Driver CR, Valway SE, Margan WM, et al. Transmission of Mycobacterium tuberculosis associated with air travel. JAMA 1994;262:1031-1035.

13. Centers for Disease Control and Prevention. Update: Outbreak of Legionnaires’ disease associated with a cruise ship. MMWR 1994;43:574-575.

14. Dickens DI, DuPont HC, Johnson PC. Survival of bacterial enteropathogens in the ice of popular drinks. JAMA 1985;253:3141-3143.

15. Cabelli VJ, Dufour AP, McCabe LJ, et al. Swimming-associated gastroenteritis and water quality. Am J Epidemiol 1982;115:606-616.

16. Cruickshank FM, Gotlin R, Jennett B. Air travel and thrombotic episodes: The economy class syndrome. Lancet 1988;2:497-498.