Philosophical Thoughts On Travel Medicine As a Specialty

David Shlim MD

It's been almost thirteen years since travel medicine practitioners first convened in Zurich, Switzerland to talk about the problems of giving health advice to travelers. Professor Robert Steffen, who hosted that first meeting, expected forty or fifty people to attend. Four hundred people showed up. The International Society of Travel Medicine was born at the next meeting in Atlanta in 1991, with attendance of 800 people. Attendance grew in subsequent meetings, reaching a high of over 1800 people at the last meeting in Montreal in 1999. This strikes me as a remarkable amount of interest in a field that has little formal recognition (you can't even be listed under travel medicine in most telephone books in the USA), and few full-time practitioners. Although a busy travel medicine practice may supplement the income of a physician, and provide interesting full-time employment for nurses or nurse practitioners, there are only rare examples of people for whom travel medicine is truly a career.

So, if travel medicine is not a career for most people, what is it? In some ways, the most relevant model is that of a hobby, analogous to bird watching. When we get together at meetings, we find that we enjoy talking about interesting sightings—typhoid fever from India, malaria from Indonesia, trypanosomiasis from Tanzania. We are comparing our life lists—as birders keep track of all of their sightings. None of us holds all of the knowledge relevant to the field—it's simply too vast. We frequently look to others for specialized information. Is there yellow fever risk at Iguassu Falls? Are there any areas of Thailand for which one should recommend Japanese encephalitis vaccine? What is the exact malaria situation in Laos? Does doxycyline have any long-term side effects? When we get together, we enjoy finding that we know as much as other people, or filling in the gaps in our knowledge.

The focus of travel medicine, and the philosophical center, has always been the pre-travel visit. The emphasis at this encounter is on prevention: what to eat, what to avoid, what immunizations to take, which medicines to take prophylactically, what to do about animal bites, motor vehicle safety, airline travel, how to self-diagnose and treat diarrhea, colds, or malaria, how to purify water, how to manage birth control and avoid sexually-transmitted diseases. And so on. If we were conscientious about sharing with the adventurous traveler all possible prophylactic advice, the pre-travel visit would last sixteen hours.

Even if we spend a great deal of time with the prospective traveler, there is no guarantee that it is time well spent. Elaine Jong, one of the pioneers of travel medicine, recently started reviewing the pre-travel encounter from the point of view of educational theory. Studying people after such an educational encounter leads to the conclusion that they can retain only seven new pieces of information at a given visit. If we give them thirty new pieces of information, we don't even know which seven are remembered.

Prevention is a virtue in medicine. However, in travel medicine, prevention is an illusion. We know that travelers are going to get sick and injured, and would be better off physically, and occasionally mentally, if they stayed home. From a purely risk oriented perspective, it makes more sense to talk people out of the trip than to help them prepare for it. However, travel also has benefits. A recent article demonstrated that middle-aged men at risk for coronary artery disease have a reduced risk of mortality if they have a vacation each year. (1)

Many travel medicine practitioners share in the feeling of excitement of travel to exotic places: there is no way to obtain the exact sense of a place without going there. The cacophony of sounds, or the silence of emptiness. The eyes and smiles of a new culture. The odors of waste competing with the aromas of exotic food. The jostling intensity of market places, the uncertainty of travel arrangements, the rare but intoxicating feeling one gets when one lets go of hope and fear and just flows along in new situations. There are certain destinations that never disappoint: such as the Taj Mahal in India, or the viewpoint of Mt. Everest, called Kala Pattar. People remember how they felt at these places long after they forget the diarrhea they endured to get there.

Some travel medicine practitioners have never traveled, and never will. They read the books, go to meetings, and focus on the risks. The benefit side has not yet been personally experienced. However, there are plenty of models for this in medicine—both men and women health practitioners offer advice on how to have a baby successfully without having done so themselves. Most of their clients travel either for enjoyment or employment. Those who travel for enjoyment can weigh the risks and benefits of a given journey. The travel medicine practitioner can help the traveler match the level of travel experience, level of health, and physical capability to the trip that they are contemplating. Travel medicine is at its best when, in addition to parading out the lists of risks and preventive behavior, we help the person sitting in front of us choose their trip wisely. The ability to help match the person to the trip is enhanced by having done such a journey one's self. Those who travel for business have a specific reason for going, and one can just try to optimize their preparation.

Through these thirteen years, the International Society of Travel Medicine has made amoeba-like attempts to extend a pseudopod and embrace a broader view of travel medicine. These other areas of focus include diagnosing and treating returned travelers, taking care of travelers while they travel, focusing on the special issues related to people who are visiting friends and relatives, taking care of immigrants and refugees, and most recently and appropriately, starting to focus on the health implications that tourism places on the host countries. The society ingests these attempts at diversity, but does not always digest them. Partly because some of these areas present larger and more insoluble problems than whether typhoid vaccine is indicated for a given trip. It takes the concerns beyond those of the hobbyist—the bird watcher—to continue the metaphor, to those of someone working in environmental protection, or wildlife preservation. It becomes real work.

So, instead, we retreat to where we are comfortable. Sitting with a prospective traveler in a room decorated with travel posters. We are extremely conscientious and utilize the best available resources. However, I think we are still nagged by uncertainty: how do we know the actual risks, and does our advice actually lower that risk? We fret over which anti-malarial to recommend, but then find that almost all cases of malaria in travelers occur in travelers who did not take any prophylaxis. How do we reach these travelers?

Knowing when and where to recommend malaria prophylaxis is also a dilemma for the travel medicine practitioner who doesn't want to paint with too broad a brush. The risk of malaria is often measured by the rate in local people from reports of diagnoses at local health posts, whether confirmed by smear or not. The risks may be over—or under—estimated. Accurate maps of malaria risk are hard to obtain, and even harder to trust. Malaria may exist up one river valley and not in another. And it can change the following year.

Furthermore, does any degree of risk of malaria constitute a reason for giving prophylaxis? Does a risk of 1 in 100,000 warrant prophylaxis for everyone? What about 1 in a million? Do we understand risk at all? How do we measure a disease risk to travelers when there has yet to be a single case in a traveler? Is the goal of travel medicine to prevent the first case in a traveler, or to react appropriately after cases have occurred? Is a risk of 15 per 100,000 a high risk or a low risk? Is it simply up to the travel medicine practitioner to draw these lines? We know that some practitioners recommend almost all vaccines and prophylactic measures in all circumstances, figuring that the only errors are in not giving something. Others are more circumspect. Are the outcomes different among patients leaving both types of practitioners?

If we are "bird watchers", then perhaps we need to create a more accurate atlas of sightings. The Geosentinel Network is an incredible start to this effort, but is currently focused on recognizing and reporting new or unexpected risks. We need to create a mechanism of sharing all case reports, linked to the probable country of origin of the disease. The extraordinary effort that Mary Wilson made a decade ago to map diseases according to geographic origin should be continued, with a focus on the specific risk to travelers.

I think that we have matured as both a society and a field sufficiently to place closer scrutiny on the advice we have traditionally given, and the sources of information we have traditionally used. We spend many hours a year counseling travelers on how to avoid diarrhea, without any evidence that we are preventing even a single case of traveler's diarrhea. We even have occasional evidence to the contrary—that pre-travel counseling makes no difference as to whether a traveler gets diarrhea. Maybe this time should be spent teaching self-diagnosis and treatment of traveler's diarrhea. It may be that the pre-travel visit of the future may not resemble our current model—or our current model may be confirmed as the best possible way to prepare travelers. We won't know until we examine our assumptions critically.

It will be an exciting adventure to try to knit up the loose ends of our knowledge. Our society embraces a wide breadth of resources: tropical medicine specialists, infectious disease practitioners, public health officials, epidemiologists, vaccinologists, virologists, occupational medicine practitioners, gastroenterologists, refugee workers, family practitioners, nurses, and many others. If we learn to ask the critical questions, we may be able to get to more beneficial recommendations, and more satisfying answers to our patients questions. Doing so will help turn our hobby into a more professional endeavor.

We may have had a fresher, more open approach to our problems at the beginning. At the end of four hours of discussion on malaria prophylaxis at the Zurich meeting, Dr. David Bradley concluded by saying, "If the previous discussion seems clear and to the point to anyone here, then they clearly haven't been listening."

1 Gump BB, Mathews KA. Are vacations good for your health? The 9 year mortality experience after the multiple risk factor intervention trial. Psychosom Med 2000; 62: 608-612.

2 Zuckerman JN, Steffen R. Risks of hepatitis B in travelers as compared to immunization status. J Travel Med 2000;7:170-174.

Dr. Shlim has organized a travel medicine conference for this summer in Jackson Hole, Wyoming that may help to accomplish the goals expressed in his editorial. Medicine for Adventure Travel 2001 will focus on "What do we know, and how do we know it?" in travel medicine. He has assembled a broad faculty of the leading thinkers in the field. The conference will look critically at our sources of knowledge in travel medicine for perhaps the first time. The meeting is July 19-24, 2001. For further information, visit the Medicine for Adventure Travel website at http://atrav.com/mat, or e-mail Dr. Shlim at drshlim@wyoming.com.