Special Feature: Bridging the World — Reports from the 7th Conference of the International Society of Travel Medicine, Innsbruck, Austria
Bridging the World—Reports from the 7th Conference of the International Society of Travel Medicine, Innsbruck, Austria
Special Feature
By Philip R. Fischer, MD, DTM&H
Awesome. Breathtaking. Gorgeous. Magnificent. Mere words seem inadequate to describe the incredible alpine setting of the 7th Conference of the International Society of Travel Medicine (ISTM) held in Innsbruck, Austria, during the last week of May 2001. The town’s name means "Bridge over the River Inn." Indeed many bridges were built and crossed during this conference.
Some 1800 participants from many different countries gathered near the banks of the fast-flowing Inn River. They were able to establish and strengthen collegial relationships while expanding their knowledge base. These multinational, multicultural, multilinguistic delegates explored the newest and most relevant medical information that can help them serve as bridges for their traveling patients who cross borders and boundaries. A few selected highlights of the meeting are noted here.
Airplanes and AEDs
Claus Curdt-Christiansen of the United Nations discussed in-flight emergencies and the use of automatic external defibrillators (AEDs). Ventricular fibrillation (VF) is the most common form of treatable cardiac arrest with an estimated 350,000 cases per year in the United States. The likelihood of survival drops by 10% for each minute the arrhythmia continues without defibrillation.
The incidence of in-flight heart attacks is estimated to be 1 per 3 billion passenger kilometers traveled, and 7% of these heart attacks are due to VF. Worldwide, there are approximately 45 cases of in-flight VF each year.
Automated external defibrillators cost "only" about $3000 and are relatively simple to use. (Tests have shown that unprepared sixth graders can successfully follow the audible directions in resuscitating manikins.) One US airline using AEDs during a 2-year period identified 200 incidents where the AED was used to evaluate a passenger. The AED advised shock to 14 travelers, and 90% of those shocked survived from their episode at least through subsequent hospital discharge. Later, review of rhythm strips showed that the AED had correctly identified each individual for whom shock was indicated and that no inappropriate shock was advised.
It is estimated that AEDs would save approximately 224 lives over a 10-year period. (Most of those affected individuals would be older than 60 years and would have underlying health problems.) The cost of using AEDs would come to about $1 million per life saved. By US law, planes with at least 1 flight attendant must have AEDs available and in use by May 12, 2004.
Airplanes and DVT
Paul Giangrande, a hemostasis-thrombosis specialist at the Oxford Radcliffe Hospital in the United Kingdom, reviewed the issue of deep vein thrombosis (DVT) in air passengers. This problem has been described in the medical literature since 1954 and has been termed "economy class syndrome." In fact, the risk of DVT is not limited to a particular part of an airplane or even to travelers sitting in airplanes; the term "travelers’ thrombosis" is probably more accurate. DVT causes discomfort and can lead to permanent limb swelling with the possibility of ulceration. Approximately 1% of DVTs are complicated by pulmonary emboli. Subsequent anticoagulant therapy is not fully benign.
There is controversy about the association between DVT and air travel,1 but there is good evidence to support the association.2,3 In addition, research has suggested that 5% of DVTs are associated with air travel and that nearly all of these occur in individuals older than 40 years on flights of more than 4 or 5 hours duration.4,5 Relative immobility is usually thought to be the major contributing factor, but there is some evidence that the relative hypoxia of the aircraft cabin might increase clotting.6
Most interesting, however, was a recent report of a randomized trial in which some passengers wore compressive stockings during flight and others did not.7 Asymptomatic DVT was found in 10% of those not using stockings and none of those using stockings; no passenger became symptomatic with a DVT, and no traveler had evidence of a pulmonary embolus.
What should air travelers do during long flights to avoid DVT? They should drink plenty of water to avoid dehydration, and they should consider elevating their legs. They should wear loosely fitting clothing, and they should exercise during the flight, either in their seats or in the aisles. In addition, stockings seem beneficial based on one study.
What about aspirin? Aspirin is known to help prevent arterial thrombosis, but there also is some indication that it might help decrease the risk of venous thrombosis.8 Pending further research, however, the indiscriminate use of medications to prevent DVT is not recommended. During the discussion after Dr. Giangrande’s presentation, the issue of sedatives was raised. Some air travelers sedate themselves to provide sleep and to help with adjustment to new time zones. When the sedative-induced sleep takes place in a sitting position without exercise breaks, there could be an increased risk of DVT.
Diarrhea Management
Herb DuPont from Texas discussed possibilities for the management of travelers’ diarrhea. He focused on fluids, diet, and nonspecific treatments and then presented a rational approach to the use of antimicrobial agents as well as his updated "algorithm" for the use of medications.
Fluids. Oral rehydration salts and solutions are frequently recommended for travelers with loose stools. Dr. DuPont reminded conference attendees that the special electrolyte mixtures might be useful for very young and very old travelers but that most any noncontaminated fluid is adequate for the hydration of most all travelers with diarrhea.
Diet. Continuing to maintain caloric and protein intake is beneficial to individuals with diarrhea. Hallway conversations in Innsbruck pursued the origin of the "myth" of the BRAT diet (bananas, rice, applesauce, toast) as part of the treatment of children with diarrhea. The origin of the myth is not clearly known, but the nonutility of this regimen is now accepted.
Symptomatic Treatment. Symptomatic treatment does not change the duration of travelers’ diarrheal illness even though it might help do so for nonbacterial endemic diarrhea in some situations. Nonetheless, bismuth subsalicylate decreases the number of stools passed by about 44%. Loperamide also decreases the number of stools passed by 41-65% in different studies, while zaldaride, a calmodulin inhibitor, decreases the number of stools passed by 29-44%.9-11 None of these medications provides a curative effect, but the symptoms may be alleviated for some.
Antimicrobial Therapy. Antibiotics clearly help shorten the illness of travelers’ diarrhea; this is apparently true even in cases where no pathogen can be identified by currently available laboratory tests. Single doses are often effective, but a full 3-day course is recommended for individuals who are not well after the first day of illness and in patients with bloody stools, temperatures higher than 39°C, or with known Campylobacter or Shigella infections. (Levofloxacin can be 500 mg per dose with twice daily dosing if this agent is continued beyond the first dose. Ciprofloxacin can be given as a single 750-mg dose or as a 500-mg dose twice daily. Norfloxacin can be given as a single 800-mg dose or as a 400-mg dose twice daily.) In Mexico, the combination of loperamide and a fluoroquinolone was more effective than the antibiotic alone.12 Increasing resistance of Campylobacter to fluoroquinolones, however, prompts consideration of other antimicrobial agents. Azithromycin is effective but does not act as quickly as fluoroquinolones.13,14 This macrolide can be used as either 1000 mg once or as 500 mg once followed, when necessary, by 250 mg on each of the subsequent two days. Pivamdinicillin is being studied as an alternative agent. Rifaximin is only negligibly absorbed, and a 400-mg dose seems as effective as ciprofloxacin.
A Management Plan. Dr. DuPont then proposed a scheme by which to manage travelers’ diarrhea medications. (Hydration, of course, remains essential.) For mild disease that does not require a change in the traveler’s activity, symptomatic therapy such as with loperamide would be used. An antibiotic (usually a fluoroquinolone or azithromycin) would be used when the diarrheal illness is significant enough to prompt a change or limitation in the traveler’s activity. If the patient is afebrile, the antibiotic would be given as a single dose in combination with a symptomatic medication such as loperamide; antibiotic doses would be given on subsequent days only if the illness persisted. If the patient was febrile or had bloody stool, a 3-day antibiotic course would be used without loperamide.
Vaccination
Vaccines were discussed by several speakers. Ann-Mari Svennerholm from Sweden noted that the live oral cholera vaccine CVD103HgR (Orochol) was 62% protective in a challenge study but was not effective in field trials in developing countries. The cholera B subunit vaccines provide only short-term cross-protection against some enterotoxigenic E coli (ETEC). Various ETEC vaccines are still being studied, but safety and efficacy data to date are encouraging. Ongoing studies with typhoid vaccine suggest that the Vi vaccine might be 55% protective up to 10 years after the dose.
Robert Chen from the CDC reviewed the cases raising concern about yellow fever vaccination in the elderly. Vaccine virus-associated deaths were noted in 2 patients older than 63 years in 1998 and in 3 since then. The CDC is planning to review the data to date obtained and might make a new recommendation soon. At the time of the meeting, however, no change was suggested in current yellow fever vaccine recommendations.
In a lunchtime meeting, Eduardo Lopez reviewed the changing epidemiology of hepatitis A as it shifts from being an infection of young children to being an infection of older children and young adults in many regions. Italy has begun routine hepatitis A immunization of children at the age of 15 months. Realizing that more than 50% of Mexican children become infected with hepatitis A by 10 years of age, one might reinforce the efforts to immunize teenagers visiting Mexico on missions trips to work with young children. Fernando Guerra from Texas noted that routine hepatitis A immunization of children in some border areas decreased the incidence of hepatitis A both in those children and in unvaccinated adults. Even at 12 months of age, hepatitis A vaccine seems well-tolerated and highly immunogenic, while not changing the response to other concurrently administered vaccines. Sheila Mackell provided an excellent review of vaccines in children and noted that hepatitis A vaccine is effective in infants who do not carry interfering maternal antibodies.
Lori Miller works with internationally adopted children in Boston. Her study of 70 children suggests that specific organism-related antibody titers should be tested in adoptees to decide which vaccines might still be needed for them.
Malaria
Ralf Bialek from Germany mentioned Bayrepel in his session on malaria in children. This product is a recently introduced aminopropanol insect repellent that has been evaluated in industry-sponsored studies. It seems to be comparable to DEET with several hours of protection afforded by a single application. Though apparently safe, Dr. Bialek noted that this compound has not been studied in young children.
Dr. Bialek also noted that experts in a few European countries are considering a change in their efforts to prevent malaria in travelers. Realizing that malaria is extremely rare in travelers to some areas, they are moving toward "standby therapy" instead of continuous chemoprophylaxis for travelers to most parts of Central and South America as well as to parts of Asia. Travelers would have to be well educated, and testing and prompt treatment for malaria would be advised. Doses of the planned presumptive treatment would be provided rather than giving prophylactic medication prescriptions. If this approach is indeed implemented, this would be a significant deviation from the current CDC and WHO recommendations for travelers to malaria-endemic areas.
Atovaquone-proguanil continues to be useful. A group from GlaxoSmithKline reported that studies in patients with compromised renal function suggest that the dose would need to be decreased in patients with a creatinine clearance of less than 30 mL/min or that an alternative agent be used. This antimalarial would not be used for people with creatinine clearances of less than 15 mL/min. This medication seems safe in the face of mild renal impairment.
Tropical Diseases
Conference participants seemed particularly interested in learning more about diseases that are prominent at various travel destinations. Guenael Rodier reviewed some of the emerging diseases. The Ebola outbreak in and near Gulu, Uganda, was declared over on Feb. 27, 2001. There were a total of 425 presumptive cases with 224 deaths, and 31 health workers were infected.
The CDC’s Steve Ostroff described "microbes in motion." Lassa Fever hit headlines as 4 cases were "imported" to Europe last year; all died. These cases illustrated the potential for virus to spread widely. For a 23-year-old German who acquired Lassa Fever in West Africa, 232 potential contacts were identified. The 32 close contacts were treated with ribavirin; one seroconverted but, with treatment, remained asymptomatic.
Ostroff also updated conference participants about the leptospirosis outbreak in athletes involved in the EcoChallenge 2000 competition on the island of Borneo. There was a 42% attack rate, and most of the infected were hospitalized for care. Swimming in the Segema River seemed to be the primary risk factor. Incidentally, doxycycline used for malaria prophylaxis seemed to protect against developing leptospirosis.
Finally, Ostroff reviewed the still puzzling outbreak of histoplasmosis among students on spring break visiting a particular hotel in Acapulco, Mexico, in March 2001. A total of 238 students fulfilled the case definition. Pending further investigation, the CDC has advised that US citizens not stay at the Calinda Beach Hotel.
Meningococcal disease was ably reviewed by Keith Cartwright of the United Kingdom. Due to the recent outbreak of a particularly virulent W-135 serogroup infection related to this year’s Haj, even Europeans are opting for the quadrivalent (A, C, Y, W-135) vaccine instead of the bivalent (A, C) vaccine.
From Amsterdam, Frank Cobelens reviewed tuberculosis in travelers. Among long-stay travelers (3-12 months), Cobelens noted that there were 3.5 PPD conversions per 1000 person-months of time in a developing country. This risk is similar to that of residents in highly endemic countries. Health care workers providing direct patient care were at particular risk of becoming infected with tuberculosis. Diagnosis of these latent TB infections is vitally important, and medical therapy is 90% effective in preventing progression to symptomatic disease.
Migrants and Immigrants
The ISTM is placing a growing emphasis on the care of migrants and immigrants. In a moving keynote address, Karl Neumann, currently of New York, displayed his own life as an example of human migration.
Louis Loutan, the incoming ISTM president, introduced a plenary session about migration medicine noting that there are 150,000,000 immigrants and refugees in the world today and that 50,000,000 of these have been displaced against their wills. More than half of the so-called "tropical" diseases occurring in the United States and Europe are in foreign-born residents, new immigrants, and people who have visited friends and relatives in other countries.
Manuel Carballo of the WHO’s International Office of Migration discussed ways in which the Balkan conflict influenced humanitarian policy. Even though war is not unusual (the majority of African countries face current or recent wars) and tragedy happens (more than 2 million Congolese have died as a result of recent wars and displacements), the Balkan conflict was closer to "home" for those who influence policy. In industrialized nations, people similar to ourselves and our neighbors were seen suffering nightly on media reports. The result has been an ongoing, potentially sustainable effort to attend to the plight of migrants everywhere.
A monument to immigrants in Canada in 1847, Doug MacPherson explained, says they "carried nothing with them other than their diseases." In this millennium, immigrants might indeed come with chronic medical problems such as hypertension and diabetes as well as an infectious condition or two. However, as providers both receive and care for migrating people, we realize that they bring much more than their bodies and their medical conditions. They bring culture and diversity, skills and abilities, experience and insight. Together, stable and migrating populations can work for common good.
Onward
The sky served raindrops for breakfast on the final day of the ISTM conference in Innsbruck. Quickly though, the sun returned and chased the retreating puffs of cloud back up into the Alps. The day became bright as the conference moved toward completion. Personal and professional bridges had been built during the conference, and the future of the ISTM, like springtime in Austria, is bright.
A certification exam is being prepared by which doctors and nurses interested in travel medicine will be able to document their knowledge of the field. Details, as they evolve, will be available at the ISTM web site (www.istm.org). The "body of knowledge" covered on the exam will be detailed in the Journal of Travel Medicine, and training courses will be identified. The first exam will be offered in conjunction with the 8th Conference of the International Society of Travel Medicine in New York, May 7-11, 2003.
References
1. Geroulakos G. The risk of venous thromboembolism from air travel. BMJ. 2001;322:188.
2. Sarvesvaran R. Sudden natural deaths associated with commercial air travel. Med Sci Law. 1986;26:35-38.
3. Clerel M, Caillard G. Thromboembolic syndrome from prolonged sitting and flights of long duration: Experience of the Emergency Medical Service of the Paris airports. Bull Acad Natl Med. 1999;183:985-997.
4. Giangrande PL. Thrombosis and air travel. J Travel Med. 2000;7:149-154.
5. Ferrari E, et al. Travel as a risk factor for venous thromboembolic disease: A case-control study. Chest. 1999;115:440-444.
6. Bendz B, et al. Association between acute hypobaric hypoxia and activation of coagulation in human beings. Lancet. 2000;356:1657-1658.
7. Scurr JH, et al. Frequency and prevention of symptomless deep-vein thrombosis in long-haul flights: A randomized trial. Lancet. 2001;357:1485-1489.
8. Prevention of pulmonary embolism and deep vein thrombosis with low-dose aspirin: Pulmonary Embolism Prevention (PEP) trial. Lancet. 2000; 355:1295-1302.
9. Okhuysen PC, et al. Zaldaride maleate (a new calmodulin antagonist) versus loperamide in the treatment of traveler’s diarrhea: Randomized, placebo-controlled trial. Clin Infect Dis. 1995;21:341-344.
10. Kaplan MA, et al. Loperamide-simethicone vs. loperamide alone, simethicone alone, and placebo in the treatment of acute diarrhea with gas-related abdominal discomfort. A randomized controlled trial. Arch Fam Med. 1999;8:243-248.
11. Silberschmidt G, et al. Treatment of travellers’ diarrhoea: Zaldaride compared with loperamide and placebo. Eur J Gastroenterol Hepatol. 1995;7:871-875.
12. Ericsson CD, et al. Single-dose ofloxacin plus loperamide compared with single dose or three days of ofloxacin in the treatment of traveler’s diarrhea. J Travel Med. 1997;4:3-7.
13. Kuschner RA, et al. Use of azithromycin for the treatment of Campylobacter enteritis in travelers to Thailand, an area where ciprofloxacin resistance is prevalent. Clin Infect Dis. 1995;21:536-541.
14. Adachi, et al. Presented to ASTMH. Houston, Tex. 2000.
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