Introduction to Infections Associated With International Travel and Outdoor Activities

Illness in Returned Travelers

GeoSentinel is a network of 53 tropical or travel disease units in 24 countries that collaboratively contribute data to a central database on travel-associated illnesses seen in patients at their units. In a published report by Leder et al. the GeoSentinel database, records of 42,173 ill returned travelers seen between 2007 and 2011 were reviewed. Typical diseases in returned travelers were categorized according to region, travel reason and patient demographic characteristics; the pattern of low-frequency travel-associated diseases was also described. The most common regions where illnesses were acquired were Asia (32.6%) and sub-Saharan Africa (26.7%). Gastrointestinal illness accounted for about 34% of travel-related illnesses, followed by febrile illness (23.3%), dermatologic diagnoses (19.5%), and respiratory illness (10.9%). The proportion of major syndromic groupings for gastrointestinal, febrile, dermatologic, and respiratory illnesses among ill returned travelers is shown in Fig. 62.2 .

There were regional differences in the frequencies of a given diagnosis: in Asia, dengue fever, typhoid fever, and bacterial pneumonia (in descending order) were the leading causes of illness, followed by hepatitis A and malaria; in the Pacific, hepatitis A was the leading diagnosis, followed by malaria and then bacterial pneumonia; in Africa, malaria was the most frequent diagnosis, followed by bacterial pneumonia and typhoid fever; in the Middle East and Latin America, respectively, typhoid fever and malaria were reported. When the GeoSentinel data were analyzed by mode of transmission, more than 35% of the diseases were vectorborne, almost 25% were respiratory, and approximately 23% were foodborne and/or waterborne.

Returned travelers presenting with acute febrile illnesses warrant prompt medical attention: malaria (especially when caused by Plasmodium falciparum ) can rapidly progress to a life-threatening condition. The early clinical signs and symptoms of several serious febrile illnesses among returned travelers are similar—however, malaria should be at the top of the list if a patient’s travel included a malaria-endemic region.

Travelers’ diarrhea is a well-known scourge of international travelers, and commonly episodes are experienced during the trip rather than after return home. Travelers to regions with suboptimal sanitation and sewage treatment systems may experience acute onset of loose watery stools sometimes accompanied by abdominal cramps, anorexia, nausea, and general malaise: this symptom complex is called travelers’ diarrhea (TD). This is usually a self-limited disease that runs its course over 5 to 7 days, but it can seriously affect the enjoyment of a short vacation trip, threaten the success of a business trip, and impair the performance of participants in competitive sports. In some cases, episodes of travel-associated diarrhea may cause lingering symptoms that prompt the traveler to seek a full medical workup after returning home. TD is dreaded by most travelers, but other gastrointestinal (GI) pathogens can cause serious, even life-threatening illnesses: cholera, typhoid, paratyphoid, and viral hepatitis fall into this category.

Diseases acquired by inadvertent contact with animals, insects, and the outdoor environment must be considered in the case of rural travelers and sometimes urban travelers as well. This category of infections includes yellow fever and other arboviruses (e.g., dengue, chikungunya tick-borne encephalitis, West Nile, Japanese encephalitis), rabies, Lyme disease, leptospirosis, and primary amebic meningoencephalitis.