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Journal of Travel Medicine 1999

GIDEON Computer Program for Diagnosing and Teaching Geographic Medicine.

Dr. Jay Keystone.

Reproduced from Review for The Journal of Travel Medicine (J Travel Med 1999  Jun;6(2):152-4)

Geographic medicine has many facets of which travel and tropical medicine are but two. Travel medicine practitioners by and large are expected to maintain the health of travellers through appropriate and up-to-date pre-travel health advice. To do this, they are expected to know something about the global epidemiology of infectious disease such as the distribution of vaccine preventable infections, of some arthropod-borne infections (malaria and dengue) and a few well known parasitic infections such as schistosomiasis and leishmaniasis. However, many travel medicine practitioners are not involved in the care of ill-returned travellers, leaving this to the infectious disease consultant and/or the expert in clinical tropical medicine. In this regard, the diagnosis of illness in returned travellers requires a knowledge of the geographic incidence of likely diseases, the likelihood of exposure to infection and the clinical features of each disease. Unfortunately, for those travel medicine practitioners who wish to be more involved in the diagnosis and management of illness in returned travellers, there are few good sources in the medical literature which provide both a clinical and epidemiological approach to the patient. Mary Wilson’s excellent text (1) “A World Guide to Infections” provides a comprehensive country-by-country review of endemic infectious diseases as well as a brief clinical summary of each infectious disease entity. However, as might be expected in a textbook, the two are not linked.

The advantage of the computer program, in this case GIDEON, is that it can link the clinical aspects of disease with its epidemiology and formulate a differential diagnosis for an illness in the returned traveller. Since its commercial release in 1991, GIDEON (Global Infectious Disease Epidemiology Network) has been advertised to practitioners as a computer program for “diagnosis simulation and informatics in geographic medicine”. (2) It was designed to diagnose and simulate any infectious disease worldwide or to identify any species of bacterium or yeast. Additional modules follow the global and country-specific status of all infectious diseases as well as the pharmacology and usage of all antiinfective drugs and vaccines. This reviewer will focus on the clinical and epidemiological aspects of the program and leave the identification of microorganisms to those with more expertise.


The diagnosis module generates a ranked differential diagnosis based on country of disease acquisition, signs, symptoms, patient demographics, laboratory data, exposure history and incubation. The user may select any number of disease features or travel itinerary by mouse click. The resulting differential diagnosis is generated by a Bayesian matrix which examines both disease incidence and symptoms prevalence within each specific disease. Two previous blinded studies have examined the performance of the GIDEON diagnosis module. In one study by the authors of GIDEON the correct diagnosis appeared in the differential diagnosis list for 94.7% of 495 cases and was ranked first in 75%. (3) The second study of 86 hospitalized patients demonstrated 69% correct diagnosis within the differential and in only 60% of cases did it rank it as first. (4)

Although I have had considerable experience using GIDEON over the past two years, I chose 10 clinical scenarios from actual case files to test the program’s accuracy in diagnosis (potential large beta error). These cases included malaria, typhoid, tuberculosis, cutaneous larva migrans, dengue fever, schistosomiasis, tick typhus, loiasis, cysticercosis and cutaneous leishmaniasis. For loiasis GIDEON was provided with the typical features but no laboratory information except for eosinophilia with loiasis. The GIDEON program correctly ranked 8 of the 10 as its first diagnosis and included the remaining two in the differential diagnosis. The differential diagnosis for these conditions could vary from as few as 9 conditions to as many as 169.

Although the differential diagnosis was apparently in rank order, it was not clear to this reviewer why some infections ranked much ahead of others. For example, in a returned traveller from Kenya with fever, splenomegaly and myalgia, malaria was correctly ranked at the top, followed in order by toxoplasmosis, HIV, leptospirosis, dengue, typhoid and typhus. My experience with GIDEON suggests that it would be helpful for the user to have some basic knowledge of infectious disease in order to appropriately utilize the differential diagnoses generated by GIDEON. Even though one must consider the ranking of a differential diagnosis with a critical eye, the advantage of GIDEON is the completeness of the differential diagnosis; the program often contains a few rare conditions which might not have been considered initially. Unfortunately, when encountering common tropical diseases with atypical findiings, GIDEON does not do as well in the provision of an appropriate differential diagnosis.


The major strength of GIDEON is its large data base which contains over 10,000 country-disease summaries. This module may be used to access data on the clinical and epidemiological profile for any one of over 230 diseases. Using the disease list, one can determine the global distribution of an infection instantaneously the status of the infection in a particular country. A very useful option generates lists of infections based on epidemiological profile. This is particularly helpful when one suspects the mode of acquisition of infection. For example, if a febrile patient returning from Zimbabwe gives a history of tick exposure, GIDEON will provide a list of all the tick-borne diseases or, specifically, tick-borne viral infections of Zimbabwe (or almost any other country of the world). In the 1998 version which I reviewed, country-by-country disease information could be as up-to-date as 1997 or as old as 1994, depending on whether the W.H.O. or the literature provided recent information. Another part to this module which impressed me was the section providing more detailed information on “diseases having global impact”. These include such infections as malaria, HIV, cholera and yellow fever. In the malaria section, one can pull up a list of countries in which chloroquine-resistant malaria occurs and obtain more detailed information on the epidemiology of drug resistant malaria in each country.


The therapy module provides the pharmacology and usage of vaccines and anti-infective agents, the latter by generic or proprietary name. The dosage for adults and children, adverse effects, CSF penetration, dialysis adjustments, drug interactions and spectrum are included for each agent. I was impressed by the extensive lists of proprietary and generic names which could be easily cross-referenced at the touch of a key stroke. Many travellers return with a list of proprietary named drugs which were administered overseas and the practitioner is stuck with the task of trying to figure out what was prescribed. For example, in GIDEON, for tinidazole, trimethroprim and tetracycline, I found 11, 25 and 184 trade names, respectively. In reviewing the treatments recommended by GIDEON, the most up-to-date therapy is usually provided. For example, in the treatment of scabies, ivermectin is indicated; however, details on how to administer topical preparations such as permethrin are not provided. The vaccine module, on the other hand, presents dosing and booster schedules, but in a rather superficial manner.

In summary, GIDEON is a very useful diagnostic tool for geographic medical conditions, but must be evaluated with a critical eye, particularly the ranked differential diagnoses and diagnoses obtained when clinical presentations are atypical. The epidemiological module is particularly useful in formulating a differential diagnosis based on country-by-country exposure. Both of these modules, and in fact, the therapeutic one, are excellent teaching tools for trainees. The therapy modules provide important useful information at a glance but provide little detail.

This program is highly recommended for travel medicine, tropical medicine, and infectious disease practitioners, particularly those residing in teaching institutions. The current price of GIDEON is $895.00 U.S., (includes the program plus one year of updates) with discounts offered for multi-year or multi-user subscriptions. If this is too dear, for those whose currency (e.g. the Canadian dollar) is much below the U.S. dollar, I would recommend its purchase by a group practice, clinic or institution to have available for common usage. In particular, teaching institutions could avail themselves of the extraordinary diagnostic and teaching capabilities of this enormous, continuously updated data base. This program does what textbooks cannot, and does it well!


1. Wilson ME. A world guide to infectious diseases, distribution, diagnosis. Oxford U Press, N.Y., 1991.

2. Berger SA  GIDEON: A computer program for diagnosis, simulation and informatics in geographic medicine. Infect Dis in Clin Pract, 1998;7:383-386

3. Berger S, Blackman U. Computer program for diagnosing and teaching geographic medicine. J Trav Med 1995, 2:199-203

4.Ross JJ, Shapiro DS. Evaluation of the computer program GIDEON for the diagnosis of fever in patients admitted to a medical service. Clin Infect Dis 1998;26:766-7