Travel Risks: Update on Traveler's Diarrhea and Other Common Problems

As international travel becomes more economical and commonplace, primary care providers are increasingly called on to help prevent related health problems. Most of these problems can be avoided by taking appropriate measures.

In previous articles (CONSULTANT, August 2001, page 1289, and September 1, 2001, page 1431), I focused on travel-specific immunizations and malaria prophylaxis, respectively. Here I discuss protection against traveler's diarrhea, motion sickness, jet lag, altitude sickness, heat- and sun-related conditions, accidents, and sexually transmitted diseases (STDs). I also address the specific hazards of travel for patients with chronic health conditions, such as diabetes and cardiovascular disease.

TRAVELER'S DIARRHEA
The most common travel-related illness is diarrhea. The risk depends on the destination. At highest risk are persons who travel to Africa, Asia, and Latin America (20% to 50% risk). The risk is more moderate for those going to the Mediterranean or Caribbean regions (8% to 20% risk). Even those who visit the United States, Canada, northern Europe, and Australasia still face limited risk (up to 8%).¹

Although diarrhea is commonly viewed as a minor problem, it can have a significant effect on business or pleasure trips. At least 20% of travelers who contract diarrhea spend part of their trip bedridden, and 40% change their itinerary because of diarrhea.² Causes of traveler's diarrhea include enterotoxigenic Escherichia coli (which usually produces a self-limited illness that lasts only a few days), Campylobacter,Shigella,Salmonella, viruses, and parasites.

Prevention. Educate patients about basic preventive measures (Table 1). Simple hygiene and safety measures-such as frequent hand washing with soap and water, use of bottled water for drinking and brushing teeth, and eating well-cooked, hot foods-appear to greatly reduce the risk of diarrhea. Also, advise patients to avoid consumption of foods purchased from street vendors, uncooked foods (other than fruits or vegetables that they have peeled themselves), nonbottled beverages, and unpasteurized dairy products.

Prophylaxis for traveler's diarrhea is no longer routinely recommended by most experts because of expense, possible adverse effects, and the risk of increased antibiotic resistance. Reserve prophylaxis for patients who may be forced to eat in areas where the safety of food and beverages is questionable, for those with reduced immunity, and for those in whom the potential consequences of illness could be profound. In such cases, preventive antibiotic therapy for adults consists of one of the following regimens, which should be followed daily while traveling, for a maximum of 3 weeks:

• Ciprofloxacin, 500 mg/d.

• Levofloxacin, 500 mg/d.

• Ofloxacin, 300 mg/d.

• Norfloxacin, 400 mg/d.

Another option is bismuth subsalicylate, 2 tablets 4 times daily. Because fluoroquinolones cannot be used in children under age 16 years, age-appropriate dosages of bismuth subsa- licylate are the preventive therapy of choice for younger patients (Table 2).

Treatment. For most patients, carrying medications to treat diarrhea (Box) and initiating treatment at the first sign of the condition is preferable to prophylaxis. The first step is to maintain hydration; this is especially important in children and elderly persons, who are the most vulnerable to dehydration. Advise travelers to carry packets of oral rehydration salts and to increase their fluid intake immediately if diarrhea develops.

The next step is to initiate drug therapy, which has been shown both to ameliorate symptoms and to shorten the course of the disease. (Note that drug therapy may not be necessary if diarrhea is mild; many mild cases will resolve in a few days with just fluid replenishment.) Loperamide is an inexpensive agent that usually relieves symptoms of uncomplicated traveler's diarrhea in less than 24 hours (see Table 2 for dosing guidelines). If diarrhea is severe or is associated with fever or bloody stools, antibiotics may be used. For adults, a 3-day course of a fluoroquinolone is recommended (except in Thailand and other areas with a high prevalence of fluoroquinolone-resistant Campylobacter; in these regions, azithromycin is the drug of choice). For children, a 3-day course of azithromycin is preferred. In the past, trimethoprim-sulfamethoxazole was used extensively, but because of increases in drug resistance, it is now second-line therapy.

Since bloody diarrhea can also be caused by conditions that do not respond to antibiotic therapy, such as amebiasis and hemorrhagic E coli infection, advise travelers to seek medical attention if their symptoms do not improve promptly with treatment.

WATER SAFETY
Stress to patients the importance of avoiding consumption of contaminated water during travel.In most settings, the best strategy is to drink only bottled water. If bottled water is not available, advise patients to boil water for at least 1 minute (3 minutes at altitudes above 2000 m [6562 ft]) and allow it to cool before drinking.³ Chemical disinfection with either iodine or chlorine is another option, although it changes taste for the worse. Iodine (either tincture of iodine or tetraglycine hydroperiodide tablets, which can be purchased in sporting goods stores or pharmacies) provides greater disinfection in a wider set of circumstances. Cold water should be warmed, or increased time should be allowed for the disinfectant to work. Cloudy water should be strained through a clean cloth and twice the usual number of disinfectant tablets used. Although some authorities recommend the use of 2-μm pore filters,⁴ the CDC does not, because of the lack of independently verified results of their efficacy.

MOTION SICKNESS
Common among land, sea, and air travelers, motion sickness is characterized by nausea, vomiting, pallor, and diaphoresis. It is not clear why some patients are more prone to motion sickness than others. Advise susceptible patients to travel in the center of all vehicles, fix their eyes on still distant objects, and increase airflow across the face.

In addition, medications may be used to prevent and treat motion sickness. Many are available over-the-counter, and the variety of product formulations (tablets, chewable tablets, syrups, and patches) can accommodate the preferences of virtually every patient. Table 3 lists dosages for several of the most popular agents.

Start treatment before symptoms begin, and anticipate the time needed for onset of action. Dimenhydrinate, one of the most popular products, is an excellent choice for both adults and children because it comes in standard tablets, chewable tablets, and a cherry-flavored elixir. It should be taken 2 hours before travel. The scopolamine patch is effective; it is also popular among travelers on extended cruises or bus tours because of its 72-hour duration of action. The patch works best if applied at least 4 hours before travel.

Both meclizine and promethazine offer the potential advantages of rapid onset of action and extended duration of action. Both are available in chewable tablets; however, meclizine has not been approved by the FDA for use in children. Promethazine, which can be used in children, is available as a syrup as well.

The most common side effects of all 4 of these medications are similar: drowsiness, blurred vision, and dry mouth. Scopolamine tablets are again being marketed for motion sickness prevention, perhaps because their onset of action (1 hour) is shorter than that of the patch. However, scopolamine is associated with a relatively high incidence of such side effects as visual disturbances, dizziness, and occasionally delirium. Use this drug with caution in the elderly.⁵

JET LAG
"Jet lag" refers to a cluster of symptoms experienced by patients who rapidly cross multiple time zones, thereby disrupting their body's innate circadian cycles. Symptoms include extreme fatigue, disrupted sleep cycles, alterations in mood and appetite, and GI upset. Jet lag is most pronounced in those crossing 5 or more time zones, and eastward travel is generally more disturbing than westward travel.⁶

Although treatments such as benzodiazepines and melatonin are widely promoted in the lay press, neither of these has been proved effective in randomized, controlled trials. The body clock normally resets itself, but it does so at the rate of about 1 hour per day. The most effective way to avoid prolonged jet lag is to adjust sleep and activity cycles to match those of the local environment as soon as possible. Exposure to bright daylight may help in adjusting circadian cycles after arrival, but the benefit of artificial light is unclear. Other suggestions include getting plenty of sleep before travel, avoiding heavy drinking (alcohol disrupts the sleep cycle), and not overeating. For patients who are willing to accept the risk of such side effects as amnesia, daytime drowsiness, or dizziness, you may offer a short-acting sedative-hypnotic (eg, zolpidem or zaleplon [5 or 10 mg]) to facilitate sleep for 1 or 2 nights after arrival.

MEDICAL RISKS OF AIR TRAVEL
Question all patients who plan to travel by air about any history of decreased oxygenation, especially that caused by chronic obstructive pulmonary disease. Because the PaO₂-normally 98 mm Hg at sea level-decreases to about 60 to 65 mm Hg (approximately 90% oxygen saturation) during flight, patients with a resting oxygen saturation below 90% face significant risk of deoxygenation. Ideally, they should use an alternative means of transportation.

Pregnant women are generally advised not to travel by air after 36 weeks' gestation, when preeclampsia is present, or when experiencing first-trimester vaginal bleeding.⁷

Table 4 lists cardiovascular contraindications to commercial airline flight.⁸ These guidelines are based in part on a study of airline passengers who had recent myocardial infarctions (MIs); the study results suggested that most complications occurred in those traveling within 2 weeks of an acute event. A margin of at least 3 weeks for those with uncomplicated MIs and 6 weeks for those with complicated MIs is recommended.

Other potential contraindications to air travel include pneumothorax; recent abdominal surgery; surgery that may have introduced air or gas; inner ear surgery; active infectiousdisease (eg, tuberculosis, varicella, measles); unresolved inner ear or sinus infections; and poorly controlled seizures or sickle cell anemia. Severely im- munocompromised patients should weigh carefully the risk of exposure to infectious agents before deciding to travel in closed vehicles such as airliners or buses.

Deep venous thrombosis (DVT) is another risk of air travel, especially for patients with additional risk factors, such as obesity, smoking, oral contraceptive use, or a history of DVT. Encourage all patients-but especially those at increased risk-to do isometric calf exercises, maintain adequate hydration, and walk around the cabin on an hourly basis to prevent venous stasis. Other preventive measures that may be used with high-risk patients include compression stockings and low molecular weight heparin.⁹

Patients with chronic medical conditions-such as diabetes, coronary artery disease, or epilepsy- who might require acute care during flights, cruises, or even bus tours should wear an identification bracelet and bring emergency medications in their carry-on baggage.

ALTITUDE SICKNESS
Symptoms of altitude sickness occur in more than 25% of persons who ascend rapidly to altitudes of 2500 m (8000 ft) or higher.^10,11 The incidence and severity of symptoms are related to the speed of ascent, the altitude achieved, the amount of exertion involved in the climb, and the degree of acclimation. Acute symptoms are usually limited to headache, nausea, light-headedness, and insomnia. More serious clinical syndromes such as pulmonary and cerebral edema can occur, but these are rare. Advise those traveling to high altitudes to acclimatize by staying 2 to 4 days at an intermediate altitude (1830 to 2440 m [6000 to 8000 ft]) and then ascending gradually (allowing 1 day for every 915 m [3000 ft] of ascent).

Acetazolamide, a carbonic anhydrase inhibitor that causes mild hyperventilation, is an effective prophylactic agent that is usually well tolerated. Give 125 to 250 mg twice daily, or 1 slow-release 500-mg tablet daily, beginning 24 to 48 hours before ascent and continuing for at least 48 hours after ascent. Symptoms of mild mountain sickness can be cured by descent to a lower altitude or by waiting at a constant altitude for 1 to 3 days-until physiologic acclimatization occurs. When descent is impossible or when symptoms persist, treatment consists of either dexamethasone, 4 mg q6h, or acetazolamide, 250 to 500 mg q12h.¹²

RISKS OF SUN EXPOSURE
Many travelers are at heightened risk for heat-, humidity-, and sun-related illness as a result of increased outdoor activities, the greater intensity of the sun in certain parts of the world, and the use of certain photosensitiz-ing medications that are part of the travel medicine armamentarium (eg, doxycycline, tetracycline, and sulfonamides). Caution patients who plan to travel about the risks of both heat exhaustion and sunburn; the latter causes immediate misery and also increases the risk of future melanoma.

Hats, sunglasses, and sunscreen are the key preventive measures. Although sunscreens with a sun protection factor (SPF) of 15 to 40 are generally recommended, those with an SPF of 30 or higher are preferable for tropical areas. Instruct patients to apply sunscreen every 2 hours and to reapply liberally after swimming. Suggest that travelers to hot climates wear light-colored, loose-fitting clothing and drink plenty of fluids to prevent dehydration. In tropical areas, a 1-L wa-ter bottle should be a constant travel companion!

ACCIDENTS
Accidents account for about 25% of all deaths of international travelers.¹³ The most frequent cause of death while traveling is a motor vehicle accident; drowning, homicide, and injuries related to participation in a risky sport are other major causes. Because of poor road conditions, speeding, overloaded vehicles, and poor vehicle maintenance, traffic accidents may be as much as 20 times more common in some parts of the world than in industrialized countries.⁴ Encourage patients to lower their risk of accidents by:

• Reducing vehicle speed.

• Avoiding travel by motorcycle or overcrowded buses.

• Restricting travel to daylight hours.

• Avoiding travel at times when other drivers are likely to have been drinking (such as on payday).

SEXUALLY TRANSMITTED DISEASES
The risk of STDs is high for certain travelers, especially those who are younger or unaccompanied, those who are long-term visitors, and those with a history of STDs.¹⁴ Studies of both male and female European travelers have documented frequent involvement in casual sexual encounters, condom use rates of 50% or less in such encounters, and increased rates of STDs on returning home.^15,16 The long-term consequences may be profound; studies have shown the prevalence of HIV infection among Europeans working overseas to be 100 to 500 times as high as in similar populations in their home countries.^17,18

Discuss with patients the risks of casual or commercial sex while traveling. Warn those who plan to be sexually active while abroad about the increased risk of exposure to HIV infection and other infections that are very difficult to treat. Urge condom use in all sexual encounters, and offer hepatitis B vaccination to those who have not been previously vaccinated.

CHRONIC DISEASES AND TRAVELCardiovascular disease. Cardiovascular events (including MIs and cerebrovascular accidents) are the leading cause of death for American travelers overseas; they account for 49% of travel deaths.¹³ The large number of cardiovascular deaths is believed to be primarily related to the high prevalence of cardiovascular disease in Americans in general. Studies have failed to find evidence of any increase in the risk of cardiovascular death among travelers; in fact, mortality rates among travelers are actually lower than US death rates for nontraveling persons of the same age.¹³ Advise patients with cardiovascular disease or risk factors to take any regularly prescribed medications as directed and to avoid overexertion during travel.

Diabetes mellitus. Patients with diabetes who travel internationally should be well stabilized, accustomed to performing home glucose monitoring, and experienced in managing occasional high or low blood sugar levels. Advise them to include snacks, hard candy, and glucagon in their carry-on baggage and, if possible, have them teach a traveling companion how to administer glucagon. Table 5 lists resources that provide instruction in how to adapt medication doses when crossing more than 6 time zones, how to deal with dietary challenges while traveling, and how to ask for help in a variety of languages.

TRAVEL MEDICAL INSURANCE
Many medical insurance policies provide little or no coverage for services provided overseas, and very few cover emergency medical evacuation. A growing number of insurance carriers have responded to this need by offering economical short-term policies that provide overseas medical coverage, contact numbers for locating English-speaking physicians while traveling, and medical evacuation service in case of catastrophic illness or injury. Many universities now require that faculty and students participating in overseas courses purchase such insurance.

Information on the cost and availability of travel health insurance can be obtained from commercial insurance carriers or from such Internet sites as www.travel.state.gov/medical.html.

High school and college students, recent graduates, and teachers can purchase economical travel health insurance through the Council on International Educational Exchange, 205 East 42nd St, New York, NY 10017.

References:

REFERENCES:1. Steffen R. Health risks for short-term travellers.In: Steffen R, Lobel HO, Haworth J, Bradley DJ,eds. Travel Medicine: Proceedings of the First Conferenceon International Travel Medicine, Zurich, April 5-8, 1988. London: Springer-Verlag; 1989:27-36.
2. Ryan ET, Kain KC. Health advice and immunizationsfor travelers. N Engl J Med. 2000;342:1716-1725.
3. Centers for Disease Control and Prevention.Health Information for International Travel, 2001-2002. Atlanta: US Dept of Health and Human Services,Public Health Service; 2001.
4. Thomas RE. Preparing patients to travel abroadsafely. Part 4: reducing risk of accidents, diarrhea,and sexually transmitted diseases. Can Fam Physician.2000;46:1634-1638.
5. Physicians' Desk Reference. 56th ed. Montvale, NJ;Medical Economics Co; 2002:2303.
6. Redfern PH. Can pharmacological agents beused effectively in the alleviation of jet-lag? Drugs.1992;43:146-153.
7. Stephens MB, Cava NA, Douglass A, JohnsonLH. Travel Medicine. Monograph, Edition No. 226,Home Study Self-Assessment Program. Kansas City,Mo: American Academy of Family Physicians; 1998.
8. Aviation Health Institute. Medical Contraindicationsto Air Travel: Guide for General Practitioners.Available at: http://www.aviation-health.org/guidelines_for_gps.html. Accessed September 12,2002.
9. Eklof B, Kistner RI, Masuda EM, et al. Venousthromboembolism in association with prolonged airtravel. Dermatol Surg. 1996;22:637-641.
10. Kozarsky PE. Prevention of common travel ailments.Infect Dis Clin North Am. 1998;12:305-324.
11. Honigman B, Theis MK, Koziol-McLain J, et al.Acute mountain sickness in a general tourist populationat moderate altitudes [published correction appearsin Ann Intern Med. 1994;120:698]. Ann InternMed. 1993;118:587-592.
12. Advice for travelers. Med Lett Drugs Ther. 2002;44:33-38.
13. Hargarten SW, Baker TD, Guptill K. Overseasfatalities of United States citizen travelers: an analysisof deaths related to international travel. AnnEmerg Med. 1991;20:622-626.
14. Mulhall BP. Sex and travel: studies of sexual behavior,disease and health promotion in internationaltravellers-a global review. Int J STD AIDS. 1996;7:455-465.
15. Mulhall BP. Sexually transmissible diseases andtravel. Br Med Bull. 1993;49:394-411.
16. Mendelsohn R, Astle L, Mann M, ShahmaneshM. Sexual behaviour in travellers abroad attendingan inner-city genitourinary medicine clinic. GenitourinMed. 1996;72:43-46.
17. Reid D, Keystone JS. Health risks abroad: generalconsiderations. In: DuPont HL, Steffen R, eds.Textbook of Travel Medicine and Health. Hamilton,Ontario: BC Decker; 1997:3-9.
18. Houweling H, Coutinho RA. Risk of HIV infectionamong Dutch expatriates in sub-Saharan Africa.Int J STD AIDS. 1991;2:252-257.