Fever commonly accompanies serious illness in returned travelers, and the most common life-threatening tropical disease associated with fever in returned travelers is malaria. Because an increased temperature can signal a rapidly progressive infection, clinicians must initiate early evaluation, especially in people who have visited areas with malaria in recent months (see Chapter 4, Malaria). The initial focus in evaluating a febrile returned traveler should be on identifying infections that are potentially life-threatening, treatable, or transmissible. In some instances, public health officials must be alerted if the traveler was possibly contagious while traveling or infected with a pathogen of public health importance (such as yellow fever or Ebola viruses) at the origin or destination. During an outbreak such as the Ebola epidemic in West Africa, special screening protocols may be needed. It is important to know that a specific cause for fever may not be identified in approximately 25% or more of returned travelers.
A large proportion of illnesses in returned travelers are caused by common, cosmopolitan infections (such as diarrhea, pneumonia, or pyelonephritis), so these must be considered along with unusual infections. Because the geographic area of travel determines the relative likelihood of major causes of fever, it is essential to identify where the febrile patient has traveled and lived (Table 11-3). Details about activities (such as freshwater exposure in schistosomiasis-endemic areas, animal bites, sexual activities, tattoos, or local medical care with injections) and accommodations (bed nets, window screens, air conditioning, type of dwelling) during travel may provide useful clues. Preparation before travel (for example, vaccinations and malaria prophylaxis) will markedly reduce the likelihood of some infections, so this is also a relevant part of the history.
Common Tropical Disease Causing Fever
Other Infections Causing Outbreaks or Clusters in Travelers
Chikungunya, dengue, malaria (Hispaniola), Zika
Acute histoplasmosis, leptospirosis
Chikungunya, dengue, malaria (primarily Plasmodium vivax ), Zika, enteric fever
Leptospirosis, histoplasmosis, coccidioidomycosis, leishmaniasis
Chikungunya, dengue, malaria (primarily P. vivax ), Zika
Bartonellosis, leptospirosis, enteric fever, histoplasmosis
Dengue, enteric fever, malaria (primarily non-falciparum)
Chikungunya, scrub typhus
Dengue, malaria (primarily non-falciparum)
Malaria (primarily P. falciparum ), tickborne rickettsiae (main cause of fever in southern Africa), acute schistosomiasis (Katayama fever), dengue
African trypanosomiasis, chikungunya enteric fever, meningococcal meningitis
Because each infection has a characteristic incubation period (although the range is extremely wide with some infections), the time of exposure needs to be defined in different geographic areas. This knowledge will allow the clinician to exclude some infections from the differential diagnosis. Most serious febrile infections manifest within the first month after return from tropical travel, yet infections related to travel exposures can occasionally occur months or even >1 year after return. In the United States, >90% of reported cases of Plasmodium falciparum malaria manifest within 30 days of return, but almost half of cases of P. vivax malaria manifest >30 days after return.
Presence of fever plus certain associated signs, symptoms, or laboratory findings can suggest specific infections (Table 11-4). Findings that should prompt urgent attention include hemorrhage, low blood pressure, altered consciousness, and high respiratory rate. Even if an initial physical examination is unremarkable, it should be repeated if diagnosis is not clear, as new findings may appear that will help in the diagnostic process (such as skin lesions or a tender liver). Although most febrile illnesses in returned travelers are related to infections, the clinician should bear in mind that other problems, including pulmonary emboli and drug hypersensitivity reactions, can also be associated with fever.
Fever accompanied by any of the following syndromes deserves further scrutiny, because it may indicate a disease of public health importance, where immediate infection control and containment measures are indicated:
Infections to Consider After Tropical Travel
Fever and rash
Dengue, chikungunya, Zika, measles, spotted fever or typhus group rickettsioses, enteric fever (skin lesions may be sparse or absent), meningococcemia, acute HIV infection, varicella
Fever and abdominal pain
Enteric fever, amebic or pyogenic liver abscess
Fever and normal or low white blood cell count
Dengue, malaria, rickettsial infection, enteric fever, chikungunya, Zika, acute HIV
Fever and hemorrhage
Viral hemorrhagic fevers (for example, dengue, yellow fever, Ebola, Lassa fever), meningococcemia, leptospirosis, spotted fever group rickettsial infections
Fever and arthralgia or myalgia (sometimes persistent)
Chikungunya, dengue, Zika, Ross River virus, muscular sarcocystosis, trichinellosis
Fever and eosinophilia
Acute schistosomiasis, drug hypersensitivity reaction; fascioliasis, sarcocystosis, trichinellosis, angiostrongyliasis, and other parasitic infections (rare)
Fever and respiratory symptoms/pulmonary infiltrates
Influenza and other common bacterial and viral pathogens, legionellosis, tuberculosis, acute schistosomiasis, Q fever, leptospirosis, Middle East respiratory syndrome, acute histoplasmosis or coccidioidomycosis, psittacosis, melioidosis, pneumonic plague
Fever and altered mental status/central nervous system involvement
Cerebral malaria, arboviral encephalitides (for example, Japanese encephalitis, West Nile virus), meningococcal meningitis, rabies, African trypanosomiasis, scrub typhus, angiostrongyliasis, tickborne encephalitis, rabies
Fever and jaundice
Acute viral hepatitis (A, B, C, E), yellow fever and other viral hemorrhagic fevers, severe malaria, leptospirosis
Epstein-Barr virus infection, cytomegalovirus infection, toxoplasmosis, acute HIV infection
Fever persisting >2 weeks
Malaria, enteric fever, Epstein-Barr virus infection, cytomegalovirus infection, toxoplasmosis, acute HIV infection, acute schistosomiasis, brucellosis, tuberculosis, Q fever, visceral leishmaniasis (rare)
Fever with onset >6 weeks after travel
Plasmodium vivax or ovale malaria, acute hepatitis (B, C, or E), tuberculosis, amebic liver abscess, melioidosis, African trypanosomiasis
Travelers visiting friends and relatives (VFRs) often do not seek pretravel medical advice and are at higher risk for some diseases than other travelers. A review of GeoSentinel Surveillance Network data showed that a larger proportion of VFRs than tourist travelers presented with serious (requiring hospitalization), potentially preventable travel-related illnesses (see Chapter 9, Visiting Friends & Relatives: VFR Travel).
Clinicians have access to resources on the Internet that provide information about geographic-specific risks, disease activity, and other useful information, such as drug-susceptibility patterns for pathogens. Infectious disease outbreaks are dynamic, as demonstrated by the Ebola epidemic in West Africa in 2014–2015, introduction and spread of chikungunya virus in the Americas beginning in late 2013, nosocomial spread from travel-associated MERS in Korea in 2015, and the rapid spread of Zika virus in the Americas in 2015 and 2016. In contrast, because of the wide use of vaccine, hepatitis A infection is now infrequently seen in US travelers.
Infections with typical seasonal transmission in the United States may occur at different times of the year (or throughout the year) in the tropics and subtropics. For example, influenza transmission can occur throughout the year in tropical areas, and the peak season in the Southern Hemisphere is April to September; clinicians in the Northern Hemisphere must be alert to the possibility of influenza outside the usual “winter” influenza season.
Travelers may acquire infections caused by bacteria resistant to commonly used antibiotics (see Antimicrobial Resistance in this chapter). Bacteria that produce extended-spectrum β-lactamases and carbapenem-resistant Enterobacteriaceae, including bacteria expressing the metalloprotease NDM-1, have been found in infections acquired during travel, most often related to medical care (both elective and emergency). Travelers to South and Southeast Asia are at high risk of acquiring multidrug-resistant Enterobacteriaceae. Enteric fever (typhoid or paratyphoid fever), has become increasingly resistant to fluoroquinolones and third-generation cephalosporins and azithromycin in some regions (see Chapter 4, Typhoid & Paratyphoid Fever).
Mary Elizabeth Wilson