Chapter 5Post-Travel Evaluation

Carlos Franco-Paredes, Natasha Hochberg

ASSESSING RISK OF ILLNESS IN TRAVELERS

An estimated 15%–70% of international travelers returning to the United States have a travel-related illness. Most travel-related illnesses are mild, but 1%–5% of travelers become sick enough to seek medical care. Although some illnesses may begin during travel, others may occur weeks, months, or even years after return. Therefore, a history of travel, particularly within the previous 6 months, should be part of the routine medical history for every ill patient, especially those with a febrile illness. A detailed history can help assess the risk of illness in a returning traveler (Box 5-01). Clinicians should consider the public health implications of certain infections (such as tuberculosis, measles, and viral hemorrhagic fever) and notify appropriate public health authorities.

A newly returned, ill international traveler should be preferentially evaluated by a physician versed in travel-related illness. For example, a febrile patient should be seen by an infectious disease or tropical medicine specialist. For assistance in finding a provider who practices clinical tropical medicine, access the consultant directory of the American Society of Tropical Medicine and Hygiene website for a listing by country and state/province (www.astmh.org) or the searchable clinic directory of the International Society of Travel Medicine (www.istm.org). For assistance with the diagnosis and management of parasitic infections, the CDC’s Division of Parasitic Diseases and Malaria’s on-call clinicians can be reached by calling 404-718-4745 for non-malaria parasitic infections or 770-488-7788 (toll-free at 1-855-856-4713) for malaria, during business hours. After business hours, on-call clinicians can be reached by calling CDC’s Emergency Operations Center at 770-488-7100.

Particular groups of travelers are considered at higher risk for illness. Travelers visiting friends and relatives are often less likely to seek pre-travel advice, obtain vaccinations, or take antimalarial prophylaxis. Adventure travelers and people visiting friends and relatives are at increased risk for becoming ill, in part because of increased exposure to pathogens. Similarly, people with underlying immunocompromised status may be at increased risk of illness, as well as atypical manifestations of disease.

TYPES OF ILLNESSES AND CLINICAL PRESENTATIONS

The most frequent health problems in ill returned travelers are persistent gastrointestinal illness (10%), skin lesions or rashes (8%), respiratory infections (5%–13%, depending on season of travel), and fever (up to 3%). A recent analysis of the GeoSentinel Surveillance Network has shown substantial regional differences in the morbidity of various syndromic categories in relation to place of exposure among ill returned travelers. For example, dermatologic problems were among the most frequent diagnoses among travelers returning from the Caribbean or Central or South America, but the diagnosis of acute diarrhea was more common for travelers returning from south-central Asia. Fever is a frequently reported complaint among returned travelers; 28% (6,957) of returned travelers seen at GeoSentinel clinics from March 1997 through March 2006 had fever as their chief reason for seeking medical care. Malaria was identified as 1 of the 3 most frequent causes of systemic febrile illness among travelers from any region.

Fever

Febrile illnesses are the most serious illnesses in travelers. Fever in a traveler returned from an area with malaria should be considered a medical emergency. The possibility of malaria as a cause of the fever should be evaluated urgently by appropriate laboratory tests and qualified personnel, and testing should be repeated if the initial result is negative. Every clinician dealing with a febrile returned traveler from an area with malaria should take steps to ensure the patient has serial blood smears evaluated on the day of presentation and should consider if there is any need for hospitalization observation.

The other most frequent “tropical” causes of fever in returned travelers are dengue, invasive bacterial diarrhea, hepatitis A, typhoid, and rickettsial infections. Other than malaria, travelers returning from sub-Saharan Africa were diagnosed most often with rickettsial infections, as well as typhoid and dengue. Nontropical illnesses, such as respiratory or urinary tract infections, also account for a large proportion of febrile illnesses in returned travelers.

In addition to a general physical examination, the clinician should look for any signs that may point to a cause of fever, including dermatologic findings (rash, insect or animal bites, eschar, localized swelling), central nervous system and ocular findings, pulmonary abnormalities, and coagulopathy. The initial evaluation of the febrile traveler should include a prompt evaluation for malaria, as well as other key tests as guided by signs and symptoms, relevant exposures, and duration of illness (Box 5-02). Acute- and convalescent-phase serologies may be needed to confirm particular diagnoses, including many rickettsial infections and dengue.

Empiric treatment for suspected serious illnesses such as malaria, leptospirosis, or rickettsial infections should always be considered when timely and accurate diagnostic testing is not available. All human malarias can be successfully treated by a course of atovaquone-proguanil or artemether-lumefantrine, and all leptospiral or rickettsial infections can be treated with doxycycline (see Chapter 3, Malaria).

Gastrointestinal Disease

Acute bacterial gastroenteritis and parasitic diarrhea, caused mostly by Giardia, are overall the most common conditions reported by travelers. Parasitic diarrhea may often present as intermittent diarrhea, nausea, headache, and fatigue but may also present with postprandial rapid expulsions of loose stool.

Persistent gastrointestinal illness in returned travelers is often caused by postinfectious irritable bowel syndrome and postinfectious lactose intolerance after an episode of travelers’ diarrhea (see the Persistent Travelers’ Diarrhea section later in this chapter). Rarely, postinfectious celiac sprue or postinfectious inflammatory bowel disease may occur after travelers have been ill with travelers’ diarrhea. Intestinal parasitic infections are uncommon causes of persistent diarrhea, although infections such as giardiasis or cyclosporiasis are often treated on the basis of clinical findings (without the benefit of laboratory confirmation).

Dermatologic Conditions

Dermatologic conditions are a very common cause of post-travel concerns, as well. Most post-travel skin ailments reported are insect bites, pyoderma, scabies, and cutaneous larva migrans.

Eosinophilia

Marked eosinophilia in a returning traveler usually indicates infection with a helminth. Diagnoses to be considered in travelers with moderate to marked eosinophilia (>1,000 eosinophils/mm³) include acute schistosomiasis or strongyloidiasis, toxocariasis, acute trichinellosis, lymphatic filariasis, loiasis, onchocerciasis, tropical pulmonary eosinophilia, fascioliasis, gnathostomiasis, angiostrongyliasis, and the larval migration of ascariasis, paragonimiasis, and hookworm.

Nonparasitic infectious causes of eosinophilia include HIV, human T-cell lymphotropic virus type 1, coccidioidomycosis, allergic bronchopulmonary aspergillosis, Mycobacterium tuberculosis, Treponema pallidum, and Bartonella henselae.

ASSESSING RISK BY INCUBATION PERIOD

Most travelers infected abroad become ill within 12 weeks after returning to the United States. However, some infections may not cause symptoms for as long as 6–12 months or more after exposure (Table 5-01). When an infectious disease is suspected, calculating an approximate incubation period is a useful step in ruling out possible causes. For example, fever beginning ≥3 weeks after return substantially reduces the probability of dengue, rickettsial infections, and viral hemorrhagic fevers in the differential diagnosis. Late-appearing illnesses include chronic forms of Chagas disease, cutaneous and mucocutaneous leishmaniasis, chronic forms of brucellosis, reactivation of tuberculosis from travel-acquired latent tuberculosis infection, malaria, sequelae of schistosomiasis, and reactivation of chronic systemic mycoses, such as paracoccidioidomycosis or coccidioidomycosis.

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