‘Road map’ assists in diagnosing various illnesses in travelers

February 2006

WASHINGTON — When predicting the most probable diagnoses for illness among travelers returning from the developing world, location is key, according to a worldwide collaborative study that found significant regional differences in infectious disease trends.

GeoSentinel, a communications and data-collection network of 30 travel/tropical medicine clinics operating on six continents, provides clinicians with disease trends in particular geographic regions.

“It looks at disease patterns in those countries, so we can see what’s crossing the borders. GeoSentinel provides ongoing trend analysis as well as acute outbreak information,” David O. Freedman, MD, professor of medicine at the University of Alabama at Birmingham, said at the 54th Annual Meeting of the American Society of Tropical Medicine and Hygiene, held here.

GeoSentinel’s findings are based on clinical data collected from more than 17,000 travelers ill enough to see a physician after returning home. It formalizes anecdotal theories on trends related to travel disease and underscores the value of global disease tracking and emerging infections.

“This information gives us a blueprint of what to look for when it comes to diagnosing sick travelers, based on where they have been,” he told Infectious Disease News. “Doctors — infectious diseases specialists in particular — can use the destination-specific differences we’ve found to guide the diagnosis and treatment of ill travelers … meaning they can order the correct tests and begin the correct therapy while waiting for confirmation.”

A 1992 Institute of Medicine report, along with subsequent analyses, identified travelers as key elements in the spread of emerging infectious diseases, according to Freedman, director of the GeoSentinel project, and travel and migration are continuing to increase.

About 8% of people who travel to the developing world require medical care either during their trip or after they return, and limited data have been available to understand morbidity profiles, up until a recent study using the GeoSentinel database published in The New England Journal of Medicine. However, GeoSentinel can now provide clinicians with important information on emerging diseases, outbreaks and specifics about what diseases are more prevalent in particular destinations.

GeoSentinel travel trends

GeoSentinel consists of travel-related illness data collected between June 1996 and August 2004 from providers, Web site entries or sick travelers presenting to GeoSentinel sites. The regions included in the data are Central America (n=1,326 ill travelers), the Caribbean (n=1,115), South America (n=1,675), sub-Saharan Africa (n=4,524), Southeast Asia (n=2,793), south central Asia (n=2,403) and other developing regions (n=1,868) such as west Asia, northeast Asia, Eastern Europe, Oceania, North Africa and Antarctica.

Freedman and colleagues compared the frequency of occurrence of a wide spectrum of diseases, including malaria and dengue fever, rickettsial infection, dermatological disorders, stomach problems, parasitic infections and respiratory disorders. They found that a traveler’s destination is associated with the probability of a diagnosis of certain diseases.

“When patients present to specialized clinics after travel to the developing world, travel destinations are associated with the probability of the diagnosis of certain diseases,” they wrote in their study. “Diagnostic approaches and empiric therapies can be guided by these destination-specific differences.”

Freedman highlighted significant trends based on regional differences, which included the following:

• Systemic febrile illness with generalized symptoms occurred disproportionately among those returning from sub-Saharan Africa or Southeast Asia, acute diarrhea occurred most commonly among those returning from south central Asia and dermatologic problems occurred among those returning from the Caribbean or Central or South America;
• Malaria was one of the three most frequent causes of systemic febrile illness among travelers from every region. However, dengue is the most common febrile illness from every region except sub-Saharan Africa and Central America;
• Of those returning from sub-Saharan Africa, rickettsial infection, primarily tick-borne spotted fever, occurred more frequently than typhoid or dengue fever; and
• Travelers from all regions, except Southeast Asia, presented with parasite-induced diarrhea more often than with bacterial diarrhea.

Food ingestion or insect bites cause most of the infectious disease risks, according to Freedman. Taking proper dietary precautions and applying a DEET containing mosquito repellent at regular intervals can dramatically reduce the risk of most travel-related illnesses.

“In a world where global travel is increasingly more common and tens of millions of people from industrialized nations travel to the developing world each year for commerce, research, education, missionary and military purposes, it is more obvious than ever that travelers should seek pre-travel consultation at a specialized travel clinic before travel and especially after they travel, if they become ill,” added co-researcher Phyllis Kozarsky, MD, professor of medicine at Emory University School of Medicine in Atlanta.

Surveillance benefits

GeoSentinel provides trend analyses and enhances surveillance methods, according to Freedman. It can be used to guide diagnostic approaches and empiric therapy, prioritize pre-travel prevention strategies and update and record morbidity profiles in travelers, which all benefit disease surveillance.

Researchers are conducting ongoing trend analyses, according to Freedman. The database is growing, and the GeoSentinel program is an asset for those locations not covered by other disease surveillance systems.

Using experience gained during the 2003 severe acute respiratory syndrome (SARS) outbreaks, GeoSentinel has been gearing up with new sites in Asia to prepare for avian influenza and will continue to monitor disease trends in travelers and detect emerging infections, according to Freedman.

The electronic communications infrastructure established through GeoSentinel recently helped identify imported traveler-related cases and outbreaks of SARS from multiple locations: leptospirosis from Borneo, hantavirus from Chile, Hajj meningitis from Singapore and first-ever dengue from Easter Island.

“Surveillance and detection is one of the three main pillars of our national strategy for pandemic influenza,” he said. “Travel clinics, such as the GeoSentinel sites, are situated ideally to effectively detect emerging infections of potential global impact at their point of entry and to track trends in travel-related morbidity.”

GeoSentinel was developed through a collaboration between the International Society for Travel Medicine and the CDC. The CDC plans to use GeoSentinel travel data to enhance the information made available on the CDC’s Travelers’ Health’s Web pages, according to co-researcher Martin Cetron, MD, director of the division of global migration and quarantine at the CDC.

“This network is especially important for early detection and rapid response as well as sharing information with WHO and health ministries throughout the world,” he said. “Networks such as these are widely recognized to be a vital part of surveillance [which were] designed to promote global health and security as envisioned by new International Health Regulations recently adopted by the World Health Assembly.”

For more information:

• Freedman DO. GeoSentinel: the global surveillance network of the ISTM and CDC. Symposium 99. Presented at: 54th Annual Meeting of the American Society of Tropical Medicine and Hygiene; Dec. 11-15, 2005; Washington.
• Freedman DO, Weld LH, Kozarsky PE, et al. Spectrum of disease and relation to place of exposure among ill returned travelers. N Engl J Med. 2006;354:119-130