Travel Medicine Research—Tradition & Future Directions - April 28, 2000

Charles D. Ericsson, MD, President, International Society of Travel Medicine, Editor-In-Chief, Journal of Travel Medicine

Dr. Ericsson is professor of medicine and head of Clinical Infectious Diseases in the Department of Internal Medicine at the University of Texas, Houston, Medical Center. He's currently also President of the International Society of Travel Medicine and Editor-In-Chief of the Journal of Travel Medicine.

Please welcome Dr. Ericsson.

[APPLAUSE]

DR. ERICSSON: I want to bring you greetings from the International Society of Travel Medicine and say a few words about what we do. It's an academic, apolitical society that stresses education and research. We give out a few little grants. We have a surveillance system that looks for outbreaks, and we .stress. communication skills, such as meetings like this. If you have any interest, outside are the first announcements for the Innsbruck meeting that will be in late May, of next year.

In the International Society of Travel Medicine, we prefer to define travel medicine very broadly. Travel medicine is not just preparing tourists or even corporate people to visit exotic lands. Travel medicine includes problems of the host countries.

Host countries are not just developing countries. For instance, what impact do the Japanese have on the US when they visit us? I do not think that has ever been adequately studied. They probably bring a lot of money in, which is good, and there was a recent incident of imported measles. When Mexicans visit Houston, they bring with them a set of medical problems that change our algorithm for medical care. A young Mexican male who presents with seizures has neurocystercicosis until proven otherwise..

Military populations, "expats and "repats," and refugees are all traveling, in one form or another, and I think are appropriate to include in the definition of travel medicine.

ISTM also has a journal. Those of you who are doing research, should consider publishing your work there. Journal of Travel Medicine is indexed on Medline now. It is indexed in ISI, so it is developing an impact factor. I think it is a worthy journal.

When one thinks of travel medicine, one usually thinks of assessing risks and thinking about what travelers incur as risks, as was spelled out in Steffen and Dupont's book about travel health.

As a rule, travel health clinics are preoccupied with the highest risks: traveler's diarrhea, malaria, upper respiratory tract infections, Hepatitis A, gonorrhea and so on.. The stated risks stress infectious diseases. However these risks must to be placed in perspective, and I'll show you the following set of data for interest and to emphasize how research should emphasize controlled observations. Is it really risky to travel? Do the stated risks really mean that the traveler is going to develop the medical problem more frequently than the non traveler? You must compare risks to those that the travelers would naturally have incurred if they had stayed home.

This interesting perspective on going to war, involves 500,000 young American adults, over 6 months, in 1991, while they were in the Gulf War. The calculations show that they actually averted cases of gonorrhea or syphilis so it was safer for these young men, in this regard, to be at war, rather than stay home. More to the point these young men actually averted deaths due to things like injury, homicide, and vehicular accidents .Does the business traveler really have psychosocial problems? Compared with what? Deciding the importance of the presence of psychosocial problems demands controls for the impact of such things as jetlag or other issues that could be confused with psychosocial problems.

Putting mortality and morbidity into perspective, infectious diseases account for only a tiny part of the actual mortality or morbidity occurring in travelers. Cardiovascular disease is the most common cause of mortality among travelers. Another risk of mortality is injury, and amongst those motor vehicle injuries are common. In general, travelers either should not drive in a developing country, or they should be properly introduced to the rules of the road.

Going back to traditional approaches to preparing travelers, let us look at some of these risks in greater detail, at least traveler's diarrhea, malaria and hepatitis. Gonorrhea is under emphasized. I always try to raise the issue of sexually transmitted diseases when I'm talking to clients. I usually use Hepatitis B as a segue into emphasizing that it's also transmitted sexually. This opens up the discussion of the issues of safe sex.

DR. ERICSSON: I think you have to get into the heads of people if you're going to modify their behavior, and humor sometimes helps. I think we can do a lot more research on how to do modify behavior. We do not do a very good job of educating people about traveler's diarrhea. Instead they go someplace and eat dangerous foods anyway. It is said over and over again: education frequently fails to change behavior. And I think it's because we haven't set ourselves up to study it correctly, using Madison Fifth Avenue techniques and the folks who really understand education. I would challenge you to try to educate your patients or your clients in a more effective fashion and then measure outcomes to see if we could actually change behavior. If we can do that, then we'll have safer travelers.

Here's some of Ericsson's truisms. In general, prevention is better than self-therapy, and it's better than searching for a physician in a developing country. A common exception is traveler's diarrhea, where we do propose self-therapy, as opposed to preventative measures. We talk about self therapy in malaria, but we usually use prevention.

And then, finally, when they do come to you, because these are busy people, you will have one shot at them. You may be able to get them back for follow-up boosters. We try to get everything done in visit, if we can.

Now a few words on the big three. First traveler's diarrhea. Currently, we're advocating self-therapy, and we arm them with things like Imodium, and antibiotics like a fluoroquinolone so that they can treat themselves aggressively. With combination therapy the patient is usually minimally inconvenienced by diarrhea.

We are getting vaccine options for diarrhea. They are not here yet. Of course, we have typhoid. We probably will have a valid ETEC vaccine in the near future, and it'll probably be appropriate to use it for many people, but I would caution you that it will not be 100-percent protective of traveler's diarrhea because ETEC only accounts for 40 or 50 percent of travelers diarrhea. Shigella vaccine is also being developed but not yet ready for commercial use.

I think we have to stress with our travelers about safe food and water. But why aren't we irradiating food? It's a cultural issue. Everybody's afraid they're going to glow in the dark if they eat irradiated food. There is also the new WHO initiative to improve public health. With safe food and water, traveler's diarrhea would go away as a problem. As far as new drugs, well, there are actually botanicals that have been studied that are available. There's new antibiotics that look promising. So as bugs become resistant, hopefully we'll stay one step ahead of the game, in terms of our interventions. Watch for other approaches like efforts to help hotels in developing worlds maintain good public health services. We, in the developed world, are going to have to put the resources into improved public health in order to make it happen.

What about malaria? Everybody knows that it's a major problem in a large part of the tropical world. And our current approaches are risk assessment and recognizing that not everybody has to take malaria prophylaxis. It does not worry me if a business traveler is not taking malaria prophylaxis when he is going to be in the hotel doing work for one day and might only step out to go to supper while wearing Deet, and then leaves the airport the next day. About 30 percent of people didn't take mefloquine because of side effects. I wonder if it's not because they don't already perceive that actual risks of malaria are sometimes incredibly low and that the doctor has prescribed prophylaxis more for medical legal reasons. And as long as the client is close to medical care, I think that it is all right sometimes not to take chemoprophylaxis. We must stress personal protective measures first, and then chemoprophylaxis is the preferred general approach versus self-therapy, which is controversial.

In the future, I think we've got to aim toward public health. We need to do more mosquito control, and eventually we will have a vaccine. Such efforts are just around the corner.

What about vaccine-preventable diseases? The most common is Hepatitis A, and Hepatitis B is important, especially for expatriates. Rabies is important in special situations, when people especially children are living in endemic areas for lengthy periods of time. Typhoid fever vaccination is indicated in people who are living in endemic regions for lengthier (greater than 3 weeks) periods of time. Hopefully we won't have to worry about polio in the very near future, since hopes are high that it will be eradicated.

Regarding Hepatitis A, and its distribution, notice with Hepatitis B a somewhat similar distribution. When you overlap the two, you get a high risk area, implying that there may be room for a new product brand Twinrix, which combines Hepatitis A and B vaccine in one product.

I try to define risk and when to exclude unneeded vaccines, and yet,the equation may shift for a corporate decision to vaccinate many to avoid one expensive repatriation.

In the future the opportunity for cheap vaccines rests with DNA technology. we'll see if the cheapness with which vaccines can be made will translate to their availability in the developing world. Also, vaccine delivery systems will improve. There are already interesting studies in the literature on genetically manipulating a banana to allow vaccination without maintaining a cold chain.

This really is a global village we live in, and I think if we're really going to have an impact on safe travel, we have to think along the lines that the WHO has begun to think. In the past they emphasized a small number of diseases, and they haven't done well with these. Small pox is eradicated. But there is still plenty of yellow fever including emerging yellow fever. Although the recent epidemic of plague in India was a pseudo epidemic, there's still concern for plague. We still have pandemics of cholera. So we're not doing a really good job controlling the diseases. And I really do espouse WHO's new approach in 2000 to continue reporting, but replace specific diseases with syndromes and they stress improved public health services. If we cleaned up the environment, we might not need to practice travel medicine. Our current approach of education, vaccination, chemo-prophylaxis, and self-therapy guides our thinking now and guides research. More studies should look into how to bring about improved public health in host countries. Maybe corporate world needs to help countries to improve their public health, which will in turn improve the health of corporate travelers. There could be a partnership there, I think, that could be very useful.

Meanwhile, I would like to see people focus on more research on how to better educate people and get them to change their behavior. We'll trust the companies to keep us going with vaccination, and we are doing a pretty good job of having available new anti-microbials and other agents when we do need to prescribe prophylaxis or treatment to somebody. But with resistance right on our tails and constantly threatening the success of treatment, primary avoidance of risk factors is the way to go in the future.

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