General Approach to the Returned Traveler
The Posttravel Evaluation
As many as 43%–79% of travelers to low- and middle-income countries become ill with a travel-related health problem. Although most of these illnesses are mild, some travelers become sick enough to seek care from a health care provider. Most posttravel infections become apparent soon after returning from abroad, but incubation periods vary, and some syndromes can present months to years after initial infection. When evaluating a patient with a probable travel-related illness, the clinician should take a thorough medical and travel history, considering all the items summarized in Box 11-1. Salient points of the history, descriptions of common nonfebrile syndromes, and initial management steps are outlined below. The differential diagnosis and management for a traveler with fever (or febrile syndrome) is discussed in detail in this chapter in Posttravel Evaluation: Fever.
The Severity of Illness
As with any medical evaluation, the chief complaint and associated clinical factors are the first things to consider when approaching an ill returned traveler. Within this context, the severity of illness is not only important for patient triage but can help clinicians distinguish certain infections from one other. Is the traveler hemodynamically stable? Is the infection potentially life-threatening, such as malaria? Does the traveler have a severe respiratory syndrome or signs of hemorrhagic fever? Some suspected illnesses may also necessitate prompt involvement of public health authorities. See “Management” below for more details.
Box 11-1. Components of a complete travel history in an ill returned traveler
Date of illness onset
Location where symptoms started (while away, in transit, or after return)
Health care received for this problem (such as medications or hospitalizations) while abroad and after return
Itinerary in country
Duration of travel
Date of return from travel
Reason for travel
Visiting friends and relatives
Providing medical care
Receiving medical care
Type of accommodations and sleeping arrangements
Hotel (with or without air conditioning)
Safari accommodations (for example, lodge, luxury tent)
Modes of transportation
Ocean (scuba diving, marine life exposure)
Freshwater exposure (lake, river, stream)
Swimming pools and hot tubs
Other adventuresome activities
Insect bites (for example, mosquito, tick, sand fly, tsetse fly)
Unpasteurized dairy products
Source of drinking water (for example, tap, bottled, purified, use of ice)
Sexual activity during travel (use of condoms, new partner)
Tattoos or piercings received while traveling
Animal or arthropod bites, stings, or scratches
Known outbreaks in the countries visited
Use of travel precautions
Effective insect repellent (DEET 25%–40% or other EPA-registered product)
Adherence to malaria prophylaxis
Past medical history
Chronic medical conditions
Recent illnesses or surgeries
Herbal, complementary, and alternative medicines
Pretravel and routine vaccinations received
Tetanus-diphtheria-acellular pertussis (Tdap)
Smoking, alcohol, and illicit drug use
Recent domestic travel or prior international travel, especially within the prior 6 months
The itinerary and activities in which the traveler participated are crucial to formulating a differential diagnosis, because potential exposures differ depending on the region of travel and behaviors. A febrile illness with nonspecific symptoms could be malaria, dengue, typhoid fever, or rickettsial disease, among others. Being able to exclude certain infections will avoid unnecessary testing. A 2013 study from the GeoSentinel Surveillance Network found that the frequency of certain diseases varied depending on the region of the world visited; among travelers with fevers, malaria was diagnosed most frequently among travelers returning from Africa, while dengue was diagnosed most frequently among travelers from Asia. The duration of travel is also important, since the risk of a travel-related illness increases with the length of the trip. A tropical medicine specialist can assist with the differential diagnosis and may be aware of outbreaks or the current prevalence of an infectious disease in an area. The 2014–2015 Ebola virus epidemic in West Africa highlighted the importance of epidemiologic factors and travel itineraries in managing patients and protecting staff and the community.
Timing of Illness in Relation to Travel
Because most common travel-related infections have short incubation periods, a majority of ill travelers will seek medical attention within 1 month of return from their destination. Travelers’ diarrhea, dengue, other arboviral infections, and influenza are examples of infections with shorter incubation periods (<2 weeks). Those with slightly longer incubation periods, up to 4–6 weeks, include malaria, typhoid fever, acute HIV, viral hepatitis, and leishmaniasis, among others. Occasionally, however, infections such as malaria, schistosomiasis, leishmaniasis, or tuberculosis can manifest months or even years later. In particular, malaria should be considered in the differential diagnosis of any traveler who traveled to a malaria-endemic area within a year of presentation. Therefore, a detailed history that extends beyond a few months before presentation can be helpful. The most common travel-related infections by incubation period are listed in Table 11-1.
Underlying Medical Illness
Comorbidities can affect the susceptibility to infection, as well as the clinical manifestations and severity of illness. An increasing number of immunosuppressed people (due to organ transplants, immune-modulating medications, HIV infection, or other primary or acquired immunodeficiencies) are international travelers (see Chapter 8, Immunocompromised Travelers). In addition, a number of factors associated with travel can increase the likelihood of exacerbations of chronic conditions during or following travel such as ischemic heart disease, inflammatory bowel disease, or chronic lung disease.
Vaccines Received and Prophylaxis Used
The history of vaccinations and malaria prophylaxis should be reviewed when evaluating an ill returned traveler. Fewer than half of US travelers to developing countries seek pretravel medical advice and may not have received vaccines or taken antimalarial drugs. Although adherence to malaria prophylaxis does not rule out the possibility of malaria, it reduces the risk and increases the likelihood of an alternative diagnosis. Fever and a rash in a traveler without measles vaccination would raise concern about measles. The most common vaccine-preventable diseases among returned travelers seeking care at a GeoSentinel clinic between 1997 and 2010 included typhoid fever, hepatitis A, hepatitis B, and influenza. More than half of these patients with vaccine-preventable diseases were hospitalized.
Individual Exposure History
Knowledge of the patient’s exposures during travel, including insect bites, contaminated food or water, or freshwater swimming, can also assist with the differential diagnosis. In addition to malarial parasites, mosquitoes transmit viruses (such as dengue, yellow fever, chikungunya, and Zika) and filarial parasites (such as Wuchereria bancrofti ). Depending on the clinical syndrome, a history of a tick bite could suggest a diagnosis of tickborne encephalitis, African tick-bite fever, or other rickettsial infections. Tsetse flies are large, and their bites are painful and often recalled by the patient. They can carry Trypanosoma brucei , the protozoan that causes African sleeping sickness. Freshwater swimming or other water contact can put the patient at risk for schistosomiasis, leptospirosis, and other diseases.
Types of accommodations and activities can also influence the risk for acquiring certain diseases while abroad. Travelers who visit friends and relatives are at higher risk of malaria, typhoid fever, and certain other diseases, often because they stay longer, travel to more remote destinations, have more contact with local water sources, and do not seek pretravel advice (see Chapter 9, Visiting Friends & Relatives: VFR Travel). Travelers backpacking and camping in rural areas will also have a higher risk of certain diseases than those staying in luxury, air-conditioned hotels.
Usual Incubation Period (Range)
Incubation <14 Days
2–4 days (1–14 days)
4–8 days (3–14 days)
Encephalitis, arboviral (Japanese encephalitis, tickborne encephalitis, West Nile virus, other)
3–14 days (1–20 days)
Specific agents vary by region
7–18 days (3–60 days)
Especially in Indian subcontinent
Acute HIV infection
10–28 days (10 days to 6 weeks)
Worldwide, can also be acquired while traveling
5–6 days (2–10 days)
7–12 days (2–26 days)
Widespread, most common in tropical areas
Malaria, Plasmodium falciparum
6–30 days (98% onset within 3 months of travel)
Malaria, Plasmodium vivax
8 days to 12 months (almost half have onset >30 days after completion of travel)
Widespread in tropics and subtropics
Spotted fever rickettsiosis
Few days to 2–3 weeks
Causative species vary by region
Zika virus infection
Widespread in Latin America, endemic through much of Africa, Southeast Asia, and Pacific Islands
Incubation 14 Days to 6 Weeks
Encephalitis, arboviral; enteric fever; acute HIV; leptospirosis; malaria
See above incubation periods for relevant diseases
See above distribution for relevant diseases
Amebic liver abscess
Weeks to months
Most common in resource-poor countries
28–30 days (15–50 days)
Most common in resource-poor countries
26–42 days (2–9 weeks)
Acute schistosomiasis (Katayama syndrome)
Most common in sub-Saharan Africa
Incubation >6 Weeks
Amebic liver abscess, hepatitis E, malaria, acute schistosomiasis
See above incubation periods for relevant diseases
See above distribution for relevant diseases
90 days (60–150 days)
2–10 months (10 days to years)
Asia, Africa, Latin America, southern Europe, and the Middle East
Primary, weeks; reactivation, years
Global distribution, rates, and levels of resistance vary widely
The most common clinical syndromes after travel to developing countries include systemic febrile illness, diarrheal illness, and dermatologic conditions. These are described in more detail in the following sections of this chapter (Fever, Persistent Diarrhea in Returned Travelers, and Skin & Soft Tissue Infections). Fever in a traveler returning from a malaria-endemic country needs to be evaluated immediately.
Other common syndromes include respiratory illnesses, asymptomatic eosinophilia, animal bites and scratches, and anxiety- or stress-related conditions.
Respiratory complaints are frequent among returned travelers and are typically associated with common respiratory viruses (see Chapter 2, Respiratory Infections). Influenza is the most common vaccine-preventable disease associated with international travel. Emerging respiratory infections such as Middle East respiratory syndrome (MERS) and H7N9 avian influenza from China should be in the differential diagnosis if the travel history is appropriate and respiratory symptoms do not have a clear alternative diagnosis. In these suspected cases, local public health authorities and CDC should be alerted immediately. See relevant sections in Chapter 4 for more information on these emerging infections, and Table 11-4 for a list of febrile respiratory illnesses among travelers.
Delayed-onset and chronic cough after travel could be tuberculosis, especially in a long-term traveler or health care worker. Helminth infections that may be associated with pulmonary symptoms include Ascaris , strongyloidiasis, paragonimiasis, schistosomiasis, and hookworms (Necator or Ancylostoma ).
Eosinophilia in a returning traveler suggests a possible helminth infection. Allergic diseases, hematologic disorders, and a few other viral, fungal, and protozoan infections can also cause eosinophilia. Eosinophilia can be present in some acute illnesses during pulmonary migration of parasites such as hookworm, Ascaris , schistosomiasis, and Strongyloides .
Other parasitic infections associated with eosinophilia include chronic strongyloidiasis, visceral larval migrans, lymphatic filariasis, and acute trichinellosis. These cases may be asymptomatic but could also have associated symptoms such as a rash, swelling, or other signs of the infection. For example, during an outbreak of sarcocystosis in travelers returning from Tioman Island, Malaysia, the affected travelers had eosinophilia and myalgias and were found to have eosinophilic myositis on muscle biopsy.
Last, since parasitic infections are rare in most travelers, it is still important to entertain other etiologies, since eosinophilia can be a sign of a hematologic malignancy. See Chapter 4 for more information on specific diseases.
Animal Bites and Scratches
Travelers who report animal exposures during travel, including both bites and scratches, should be evaluated promptly for rabies exposure and provided rabies postexposure prophylaxis if indicated (see Chapter 4, Rabies). If the traveler was exposed to a macaque, herpes B virus postexposure prophylaxis may be considered (see Chapter 3, Animal Bites & Stings, and Chapter 4, B Virus).
Most posttravel illnesses can be managed on an outpatient basis, but some patients, especially those with systemic febrile illnesses, may need to be hospitalized. Furthermore, potentially severe, transmissible infections such as Ebola or MERS require enhanced infection control measures and may require higher levels of care. Severe presentations, such as acute respiratory distress, mental status change, and hemodynamic instability, require inpatient care. Clinicians should have a low threshold for admitting febrile patients if malaria is suspected. Confirmation of diagnosis can be delayed, and complications can occur rapidly. Management in an inpatient setting is especially important for patients unlikely to follow up reliably or when no one is at home to assist if symptoms worsen quickly.
Initial evaluation and common laboratory tests:
Although the chief complaint will direct diagnostic testing and management, common laboratory tests often help with the initial evaluation. These include a complete blood count with differential to look for leukocytosis, leukopenia, anemia, thrombocytopenia, and eosinophilia. A complete metabolic profile will identify electrolyte, renal, or liver dysfunction. Blood cultures and malaria rapid diagnostic tests may be needed depending on the presence of fever and travel itinerary. Last, depending on the differential diagnosis, serologic or PCR tests for arboviral infections, for example, as well as stool cultures and ova/parasite exams may be warranted.
Consultation with an infectious diseases physician is recommended when managing severe and/or complicated travel-related infections, or when the diagnosis remains unclear. A tropical medicine or infectious disease specialist should be involved in cases that require specialized treatment, such as neurocysticercosis, severe malaria, and leishmaniasis, among others.
Public health authorities may need to be involved for transmissible, high-consequence infections. CDC provides on-call assistance with the diagnosis and management of parasitic infections at 404-718-4745 for parasitic infections other than malaria or 770-488-7788 (toll-free at 855-856-4713) for malaria, during business hours. After business hours, call the CDC Emergency Operations Center at 770-488-7100. See Chapter 1, Introduction to Travel Health & the CDC Yellow Book, for additional contact information.
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Jessica K. Fairley