Infections in Returning Travelers

Of the approximately 80 million people who travel from industrialized to developing countries each year, 22% to 64% of travelers report some illness. The approach to the patient requires knowledge of world geography, the epidemiology of disease patterns in 230 or so countries, and the clinical presentation of a wide spectrum of disorders. Most illnesses are mild, most are self-limited, and many are noninfectious. Up to 10% of travelers may consult a physician during or after a trip, and approximately 1 in 100,000 travelers will die.

The ill travelers that do come to the attention of infectious diseases clinicians are generally either the most seriously ill or are suspected of harboring infectious agents not familiar in their home country. Based on 42,173 ill returned travelers seen by the GeoSentinel Surveillance Network at 53 different clinical sites on six continents, in patients presenting to infectious or tropical diseases specialists after travel to the developing world, specific travel destinations are associated with the probability of the diagnosis of certain diseases. Diagnostic approaches and empirical therapies can be guided by these destination-specific differences. Important region-specific disease occurrence data indicate that febrile illness is most important from Africa and Southeast Asia; malaria is one of the top three diagnoses from every region, yet over the past decade dengue has become the most common febrile illness from every region outside sub-Saharan Africa; in sub-Saharan Africa, rickettsial disease is second only to malaria as a cause of fever; respiratory disease is most important in Southeast Asia and sub-Saharan Africa; and acute diarrhea is disproportionately from South Central Asia. When individual diagnoses are collected into syndrome groups and examined for all regions together, 233 of every 1000 ill returned travelers have a systemic febrile illness, 334 have acute or chronic gastrointestinal (GI) infection, 195 have a dermatologic disorder, and 209 have a respiratory disorder. Recent data have also been evaluated in the context of large international events, attendance at which provides an additional common epidemiologic link by which to assess the risk of communicable diseases. Travel illness associated with attendance in Brazil for the 2014 FIFA World Cup, characterized by dermatologic conditions (40%), diarrheal syndromes (25%), and febrile systemic illnesses (dengue and malaria, predominantly caused by Plasmodium vivax ), might be expected to anticipate illnesses associated with the 2016 summer Olympic games in Brazil. Considerations specific to the Hajj would include the ingestion of camel's milk, crowding, and the spread of viral and bacterial respiratory pathogens, including Middle East respiratory syndrome–coronavirus (MERS-CoV) and drug-resistant enteric pathogens. These infections would include third-generation cephalosporin- and colistin-resistant Salmonella enterica ssp. enterica serovar Newport.

Travelers who become ill during, or any time up to several months after, a foreign trip will frequently associate that illness with a possible travel-specific cause. This may be the case, but often it is not. Routine disorders are common, and common disorders are common whether actually acquired during travel or at some time after the trip. Thus fever, sore throat, and cervical adenopathy in a college student who returned 2 weeks earlier from a developing country is still more likely to be streptococcal pharyngitis or infectious mononucleosis than diphtheria. Presented with an ill patient with a history of travel, the physician must maintain discipline in making two separate lists of differential diagnoses, the first in the context of travel, and the second considering the same presenting symptoms and signs as if in any other patient. The approach and workup must then proceed in parallel, with appropriate priority given to the most urgent or the most treatable diagnoses at the top of each list. A consideration of increasing importance is the acquisition of drug-resistant organisms in the normal bowel flora. The contribution of antimicrobial therapy and antimotility agents may be important in this regard.

In this chapter travelers are considered to be those returning from short visits to developing countries, and the term does not include immigrants, refugees, and very long-term residents arriving from those countries. Constellations of exposures and clinical presentations highly suggestive of particular diagnoses in returned travelers are shown in Table 319.1 . Highly exotic endemic diseases rarely acquired by travelers are not discussed. Low-frequency illnesses (<20 cases of the 42,173 listed in the “GeoSentinel Surveillance of Illness in Returned Travelers, 2007–11” ), some potentially serious, were reported, including visceral leishmaniasis, East African trypanosomiasis, scrub typhus, relapsing fever, angiostrongyliasis, botulism, melioidosis, tularemia, hantavirus infection, and infection with Plasmodium knowlesi. No cases of yellow fever (YF), Ebola virus, Lassa fever, Marburg virus, tetanus, polio, anthrax, or plague were reported in this particular 5-year cohort, thus attesting to their rarity outside of large-scale outbreak scenarios.

The focus is on the identification of infectious causes of the presenting illness, on travel-associated risk factors, and on manifestations of those diseases that are particular to travelers. Detailed discussions of pathophysiology, spectrum of clinical manifestations, and therapy for each infectious agent are found in the disease-specific chapters of this book. Fever, traveler's diarrhea, and skin problems are the most common presenting illnesses in returned travelers. Eosinophilia is less common but is a frequent source of referral to the infectious diseases specialist.