Multisystem Processes & Disorders

Returning traveler with fever: workup

Clinical Overview and When to Suspect Travel-Related Febrile Illness

— Malaria is the single most common life-threatening cause, especially after sub-Saharan Africa travel

— Dengue dominates returnees from Southeast Asia, Latin America, Caribbean

— Enteric fever (typhoid/paratyphoid) common after South Asia travel

— Rickettsial disease common after sub-Saharan safari travel

— Nonspecific viral, influenza, COVID-19, UTI, pneumonia still represent a major fraction — don't anchor on the exotic

— Fever within 21 days of return from endemic area

— Travel to malaria-endemic region without chemoprophylaxis or with poor adherence

— Rural travel, freshwater exposure, animal/insect bites, unprotected sex, sick contacts, IV drug use abroad

— Hospitalization or invasive procedures abroad → consider MDR organisms (CRE, MRSA)

— Identify vital-sign instability (sepsis, severe malaria, viral hemorrhagic fever)

— Identify public health threats requiring isolation (VHF, MERS, measles, TB, novel respiratory pathogens)

— Rule out malaria before committing to any other diagnosis if Africa exposure

— <14 days: dengue, malaria, leptospirosis, rickettsiae, enteric fever, influenza, chikungunya, Zika

— 14 days–6 weeks: malaria (esp. P. vivax/ovale), enteric fever, acute schistosomiasis, viral hepatitis, amebic liver abscess

— >6 weeks: malaria (vivax/ovale relapse), TB, visceral leishmaniasis, chronic schistosomiasis

Step 3 management: In any febrile returnee from a malaria-endemic region, order thick and thin smears plus rapid diagnostic test on arrival — empiric antimalarials are not a substitute for diagnosis, and a single negative smear does not exclude malaria; repeat q12–24h ×3.

Definition: Fever ≥38.0°C (100.4°F) in a patient who returned from international travel within the prior 12 months, with most tropical infections presenting within 21 days of return.

Epidemiology of returning traveler fever (GeoSentinel data):

When to suspect a serious tropical pathogen:

Initial triage priorities:

Incubation framing:

Presentation Patterns and Key History

— Timing: exact dates of departure/return, symptom onset relative to return

— Regions: countries, rural vs urban, altitude, specific itineraries (safari, jungle, beach)

— Activities: freshwater swimming, caves, farms, sexual contacts, tattoos, medical/dental care abroad

— Vaccines and chemoprophylaxis: pre-travel vaccines (yellow fever, typhoid, hep A/B), malaria prophylaxis taken and adherence

— Exposures: insect bites, animal contact, unpasteurized dairy, undercooked meat/seafood, contaminated water, sick contacts

— Local outbreaks: ongoing epidemics in visited areas (check CDC Travel Health Notices)

— Fever + jaundice: malaria, viral hepatitis, leptospirosis, yellow fever

— Fever + rash: dengue, chikungunya, Zika, measles, rickettsioses, acute HIV, typhoid (rose spots)

— Fever + eosinophilia: acute schistosomiasis (Katayama), strongyloides, filariasis, fascioliasis, visceral larva migrans, drug reaction

— Fever + hemorrhage: dengue hemorrhagic fever, VHF (Ebola, Lassa, Marburg, CCHF), severe leptospirosis, meningococcemia

— Fever + diarrhea: enteric fever, amebiasis, traveler's diarrhea bacterial, Giardia (usually afebrile), norovirus

— Fever + respiratory: influenza, COVID-19, Legionella, melioidosis, MERS, TB, Q fever

— Fever + CNS signs: cerebral malaria, Japanese encephalitis, meningococcus, rabies, neurocysticercosis, African trypanosomiasis

— Asking about prophylaxis adherence and which drug (atovaquone-proguanil, doxycycline, mefloquine) narrows risk

— Yellow fever vaccine → strongly argues against YF; typhoid vaccine is only ~50–80% effective, doesn't exclude enteric fever

Board pearl: A returnee from West Africa with fever and bleeding gums, conjunctival injection, or unexplained bruising within 21 days mandates immediate isolation and public health notification for possible VHF before further workup.

Structured travel history (the "TRAVEL" framework):

Symptom-pattern clues:

Pre-travel preparation review:

Physical Exam Findings and Hemodynamic Assessment

— Tachycardia disproportionate to fever → typical bacteremia, sepsis

— Relative bradycardia (Faget sign): classically typhoid, yellow fever, brucellosis, leptospirosis, drug fever, Legionella

— Hypotension + capillary leak in dengue defervescence phase = dengue shock syndrome (days 3–7, when fever breaks)

— Narrow pulse pressure (<20 mmHg) in dengue is an early warning sign

— Eschar (tache noire): African tick-bite fever (R. africae), scrub typhus, Mediterranean spotted fever

— Rose spots: blanching salmon-colored macules on trunk → typhoid

— Petechiae/purpura: dengue, meningococcus, VHF, leptospirosis, rickettsial

— Maculopapular rash: dengue, chikungunya, measles, acute HIV

— Conjunctival suffusion without exudate: leptospirosis

— Lymphadenopathy: acute HIV, EBV, brucellosis, leishmaniasis, trypanosomiasis (Winterbottom sign = posterior cervical nodes in African sleeping sickness)

— Pharyngitis: acute HIV, EBV, Lassa

— Hepatomegaly: malaria, viral hepatitis, amebic liver abscess, leptospirosis, visceral leishmaniasis

— Splenomegaly: malaria, enteric fever, EBV, visceral leishmaniasis (massive), brucellosis, schistosomiasis

— RUQ tenderness with referred shoulder pain: amebic liver abscess

— Altered mental status with fever from Africa → cerebral malaria until proven otherwise

— Meningismus → meningococcal, Japanese encephalitis, tuberculous meningitis

— Polyarthralgia/arthritis: chikungunya (often debilitating, persistent), dengue (less severe), parvovirus, acute HBV

Key distinction: Dengue = severe myalgia/retro-orbital pain with often-mild joint symptoms; chikungunya = prominent symmetric polyarthritis often persisting weeks to months. Both circulate in overlapping regions and can co-infect — clinical clue alone is insufficient, order serology/PCR for both.

Vital signs and hemodynamics:

Skin/mucous membrane findings:

HEENT:

Abdominal:

Neurologic:

Joint:

Diagnostic Workup — Initial Labs, Smears, and Imaging

— CBC with differential and peripheral smear (review manually)

— Thick and thin blood smears + malaria RDT if any malaria-endemic exposure — repeat q12–24h ×3 before excluding malaria

— CMP (LFTs, creatinine, electrolytes, glucose — hypoglycemia in severe malaria)

— Coags (PT/INR, PTT) and fibrinogen if any bleeding signs

— Urinalysis (proteinuria/hematuria in leptospirosis, hemoglobinuria in severe malaria — "blackwater fever")

— Blood cultures ×2 before antibiotics (enteric fever yield ~60–80% in week 1)

— HIV test, hepatitis A/B/C serologies if jaundice or risk factors

— Pregnancy test in any woman of reproductive age (alters drug choices)

— Lactate, procalcitonin if sepsis suspected

— Thrombocytopenia + fever → malaria, dengue, leptospirosis, rickettsia, enteric fever, acute HIV — extremely high yield combination

— Leukopenia: dengue, typhoid, viral infections, malaria

— Eosinophilia (>500): helminthic infection (schistosoma, strongyloides, filaria, hookworm) — bacteria/viruses suppress eosinophils

— Atypical lymphocytes: EBV, acute HIV, dengue, CMV

— Marked transaminitis (>1000) → viral hepatitis, yellow fever

— Mild AST/ALT + hyperbilirubinemia → malaria, leptospirosis

— Alk phos elevation + RUQ pain → amebic liver abscess

— CXR if respiratory symptoms (Legionella, TB, melioidosis, pneumonia)

— RUQ ultrasound for jaundice or RUQ tenderness (gallbladder wall edema in dengue/leptospirosis; liver abscess)

— CT abdomen if persistent fever and negative initial workup (occult abscess, lymphoma)

CCS pearl: On the CCS case, order blood cultures ×2, CBC with diff, CMP, UA, malaria smears + RDT, HIV, pregnancy test, and CXR as your standard returning-traveler bundle before tailoring further — advancing the clock without these will cost you points.

Mandatory initial labs for any febrile returnee:

Hematologic clues on CBC:

LFT patterns:

Imaging:

Diagnostic Workup — Advanced and Confirmatory Studies

— Thick smear = sensitivity; thin smear = species identification and parasitemia quantification

— Parasitemia >5%, schizonts on smear, AMS, ARDS, AKI, acidosis, hypoglycemia, Hgb <7, bleeding = severe malaria → IV artesunate

— RDTs detect HRP-2 (P. falciparum) and pLDH; cannot quantify parasitemia

— Days 1–7: NS1 antigen and/or RT-PCR

— After day 5: IgM/IgG serology

— Tourniquet test historical; CBC trend (rising Hct + falling platelets) signals plasma leakage

— Blood cultures first week (highest yield), stool/urine cultures weeks 2–3, bone marrow culture is most sensitive (rarely needed)

— Widal serology unreliable in endemic exposure — do not rely on it

— Serology (acute + convalescent IFA) is gold standard but retrospective

— Treat empirically with doxycycline on clinical suspicion — do not wait for confirmation

— Early: PCR on blood (first week)

— Late: MAT serology (after day 7), IgM ELISA

— Stool/urine ova — often negative in acute Katayama; serology (ELISA) is the test of choice in acute phase

— RT-PCR via CDC/state lab; isolate first, test through public health channels — do not send to routine lab

— O&P ×3, stool culture, C. difficile if antibiotic exposure, Cryptosporidium/Giardia/Cyclospora antigen

— Amebiasis: stool antigen or PCR (more sensitive than microscopy)

Board pearl: A single negative malaria smear never excludes malaria — three negative smears 12–24h apart are required. Don't be talked out of empiric IV artesunate if the patient is critically ill from a P. falciparum region.

Malaria confirmation and severity:

Dengue testing (timing-dependent):

Enteric fever (typhoid/paratyphoid):

Rickettsial disease:

Leptospirosis:

Schistosomiasis (Katayama fever):

Viral hemorrhagic fever:

Stool studies:

TB workup if cough, weight loss, prolonged fever: sputum AFB ×3, IGRA, CXR/CT

Lumbar puncture for any AMS or meningismus — after head CT if focal signs

Risk Stratification and Disposition Logic

— Falciparum malaria (kills within 24–48h)

— Meningococcemia

— Viral hemorrhagic fever (isolation, public health)

— Typhoid with complications (GI perforation, encephalopathy)

— Sepsis from any source

— qSOFA ≥2, lactate ≥2, hypotension → ICU/stepdown

— Severe malaria criteria (WHO): impaired consciousness, prostration, convulsions, ARDS, shock, DIC, hemoglobinuria, jaundice + parasitemia, AKI, hypoglycemia <40, severe anemia, parasitemia ≥5%

— Dengue warning signs: abdominal pain, persistent vomiting, mucosal bleeding, lethargy, hepatomegaly, rising Hct with falling platelets — admit

— ICU: severe malaria, septic shock, ARDS, dengue shock syndrome, suspected VHF, cerebral involvement

— Floor admission: moderate parasitemia, dengue with warning signs, enteric fever needing IV antibiotics, undifferentiated fever in immunocompromised, pregnancy, comorbidities

— Outpatient with close follow-up: clinically well, low parasitemia uncomplicated P. vivax/ovale/malariae after first dose observed, uncomplicated dengue without warning signs, mild traveler's diarrhea, confirmed self-limited viral syndrome

— Start empiric artesunate IV before confirmation if classic severe malaria picture from endemic area

— Start empiric doxycycline if rickettsial features (eschar, fever, rash, exposure)

— Start empiric ceftriaxone if suspected enteric fever or undifferentiated sepsis pending cultures

— Respiratory isolation: TB, MERS, measles, novel respiratory viruses

— Contact + droplet + airborne (special VHF protocols): suspected Ebola, Lassa, Marburg, CCHF

Step 3 management: Pregnancy in a malaria-endemic returnee dramatically raises maternal mortality from falciparum — admit all pregnant patients with confirmed or strongly suspected malaria regardless of initial appearance.

Step 1 — Identify "must-not-miss" diagnoses immediately:

Step 2 — Apply severity criteria:

Step 3 — Disposition framework:

Empiric treatment thresholds:

Isolation considerations:

Pharmacotherapy — First-Line Regimens by Diagnosis

— Artemether-lumefantrine (Coartem) PO first-line, OR atovaquone-proguanil, OR quinine + doxycycline

— Chloroquine reserved for confirmed P. vivax/ovale/malariae from chloroquine-sensitive areas

— IV artesunate ×24h minimum, then transition to full PO course (artemether-lumefantrine)

— Monitor for post-artesunate delayed hemolysis weekly CBC ×4 weeks

— Supportive only: IV crystalloids titrated carefully, acetaminophen (avoid NSAIDs and aspirin — bleeding risk)

— No specific antiviral

— Empiric ceftriaxone IV for hospitalized patients (rising fluoroquinolone resistance, esp. South Asia XDR strains)

— Azithromycin PO for uncomplicated outpatient

— Add dexamethasone for severe typhoid with shock/altered mentation (mortality benefit)

— Mild: doxycycline PO

— Severe (Weil disease): IV penicillin G or ceftriaxone

— Watch for Jarisch-Herxheimer reaction

Board pearl: Never give primaquine without documented G6PD level — severe hemolysis can be fatal. This is a classic Step 3 vignette.

Malaria — uncomplicated P. falciparum (or unknown species from chloroquine-resistant area):

Malaria — severe (any species, any parasitemia with severity criteria):

P. vivax / P. ovale: add primaquine (or tafenoquine) for hypnozoite eradication — check G6PD first (hemolysis risk)

Dengue:

Chikungunya/Zika: supportive; Zika in pregnancy → fetal surveillance

Enteric fever (typhoid/paratyphoid):

Rickettsial diseases (all): doxycycline 100 mg BID ×7 days — including in pregnancy and children (CDC/AAP endorsed for life-threatening rickettsial disease)

Leptospirosis:

Amebic liver abscess: metronidazole ×7–10 days, then luminal agent (paromomycin or iodoquinol) to clear cysts

Acute schistosomiasis (Katayama): corticosteroids for severe symptoms, then praziquantel after 6–8 weeks (worms must mature for praziquantel to work)

Strongyloides: ivermectin — screen before steroids/immunosuppression in any traveler from endemic area

Expanded Pharmacology and Drug Pitfalls

— Now FDA-approved (2020) and commercially available; previously CDC investigational

— Dose 2.4 mg/kg IV at 0, 12, 24h, then daily until PO tolerated

— Mandatory follow-up CBC weekly ×4 weeks for post-artesunate delayed hemolysis (PADH)

— Photosensitivity, esophagitis (take upright with water), GI upset

— Historically avoided in pregnancy/<8yo for teeth staining, but short courses (<21 days) for serious rickettsial or anthrax exposure are now considered safe per CDC/AAP

— Well tolerated, daily dosing, expensive

— Take with fatty food for absorption

— Avoid in severe renal impairment (CrCl <30)

— Neuropsychiatric side effects (vivid dreams, anxiety, psychosis) — contraindicated with seizure disorder, psychiatric history, cardiac conduction abnormalities

— Both require G6PD testing — quantitative for tafenoquine

— Tafenoquine = single-dose for radical cure; primaquine = 14-day course

— 14-day course typical for complicated cases; 7–10 days uncomplicated

— Watch for relapse (5–10%) → repeat blood cultures if fever recurs

— Resistance now >90% in South Asia — do not use ciprofloxacin empirically for South Asian enteric fever

— XDR strains may require carbapenem (meropenem) or azithromycin

— Never give steroids in a febrile traveler before excluding strongyloides (hyperinfection syndrome with gram-negative bacteremia/meningitis) — screen with serology, treat with ivermectin first

— Confirmed hepatitis A → household contact post-exposure prophylaxis (HepA vaccine or Ig)

— Confirmed measles → public health notification, contact tracing

Step 3 management: Before starting any immunosuppressive therapy (steroids, biologics, chemo) in a patient with prior tropical residence/travel, screen for strongyloides serology, TB (IGRA), HBV, HCV, HIV — a recurring Step 3 outpatient theme.

Artesunate access in the US:

Doxycycline considerations:

Atovaquone-proguanil:

Mefloquine:

Primaquine and tafenoquine:

Ceftriaxone in enteric fever:

Fluoroquinolone resistance in typhoid:

Steroid pitfalls:

Vaccine-preventable considerations post-illness:

Special Populations — Elderly and Renal/Hepatic Impairment

— Higher risk for severe dengue, severe malaria, complicated typhoid, and bacterial superinfection

— Atypical presentations: delirium may dominate over fever; relative bradycardia harder to interpret on rate-control meds

— Lower threshold for admission and ICU triage

— Drug interactions: doxycycline + warfarin (↑INR), macrolides + QT-prolonging meds, atovaquone-proguanil minimal interactions (preferred in polypharmacy)

— Atovaquone-proguanil contraindicated if CrCl <30 (proguanil accumulates → marrow toxicity)

— Quinine requires dose reduction in renal failure; risk of cinchonism (tinnitus, headache, vertigo) and hypoglycemia

— IV artesunate: no dose adjustment needed; preferred in renal failure

— Ceftriaxone: usually no adjustment, but avoid concurrent calcium-containing IV fluids in neonates

— Acyclovir-class and aminoglycosides require renal dosing if used adjunctively

— Atovaquone-proguanil, mefloquine, and artemether-lumefantrine all undergo hepatic metabolism — use cautiously, monitor LFTs

— Doxycycline can be hepatotoxic in pre-existing disease

— Acetaminophen safe at reduced doses (max 2 g/day in cirrhosis)

— Avoid NSAIDs in dengue, liver disease, or any bleeding risk

— G6PD deficiency → no primaquine, tafenoquine, dapsone, nitrofurantoin, sulfonamides

— Sickle cell disease → severe malaria still possible (heterozygote protection partial only); aggressive hydration and exchange transfusion consideration

— Higher risk for severe and atypical disease; broader differential (CMV, MAC, cryptococcus, talaromyces in SE Asia)

— Live vaccine restrictions affect pre-travel preparation — review history

Key distinction: Old age plus parasitemia ≥2% with falciparum should be managed as severe malaria even without classical end-organ criteria — elderly patients deteriorate faster and the parasitemia threshold for severity is effectively lower.

Elderly travelers:

Renal impairment:

Hepatic impairment:

Hemolysis-prone patients:

Immunocompromised travelers (HIV, transplant, biologics):

Special Populations — Pregnancy, Pediatrics, and Returning Migrants

— Malaria in pregnancy → severe maternal anemia, hypoglycemia, ARDS, fetal loss, placental sequestration of P. falciparum

— All pregnant patients with malaria are admitted, even if asymptomatic/low parasitemia

— First trimester P. falciparum: quinine + clindamycin historically preferred; artemether-lumefantrine now acceptable per updated WHO/CDC guidance when benefits outweigh risk

— Second/third trimester: artemether-lumefantrine first-line

— Severe malaria in any trimester: IV artesunate (life-saving, benefit outweighs theoretical risk)

— Primaquine and tafenoquine contraindicated in pregnancy → use weekly chloroquine prophylaxis until delivery, then radical cure postpartum after G6PD testing of mother and infant

— Doxycycline generally avoided in pregnancy; azithromycin is preferred for rickettsial disease in pregnancy when life-threatening rickettsia is not the diagnosis — but for RMSF/severe rickettsia, doxycycline is still first-line even in pregnancy

— Dengue + pregnancy → risk of vertical transmission near delivery, hemorrhagic complications

— Zika in pregnancy → microcephaly, fetal brain abnormalities — serial fetal ultrasounds, refer to MFM

— Children deteriorate quickly with malaria; cerebral malaria is a leading cause of pediatric tropical mortality

— Weight-based dosing of artemether-lumefantrine; IV artesunate dosing higher per kg in children <20 kg (3 mg/kg)

— Doxycycline now acceptable short-course in all ages for suspected RMSF or severe rickettsial disease (AAP 2019)

— Pediatric dengue: monitor closely during defervescence for shock

— Often don't take prophylaxis (perceived immunity); semi-immune adults can still get severe disease, and children born in non-endemic countries have no immunity

— Higher rates of malaria, enteric fever, TB

— Screen for chronic schistosomiasis, strongyloides, Chagas (Latin America), HBV, HCV, HIV, TB

Board pearl: A pregnant woman returning from sub-Saharan Africa with fever gets a malaria smear before anything else — falciparum in pregnancy is a true emergency.

Pregnancy:

Pediatrics:

Returning long-term migrants and visiting-friends-and-relatives (VFR) travelers:

Complications and Adverse Outcomes

— Cerebral malaria: impaired consciousness, seizures, coma — mortality 15–20% even with treatment

— ARDS: can develop or worsen after initiation of treatment (paradoxical worsening)

— AKI from hemoglobinuria ("blackwater fever") and acute tubular necrosis

— Hypoglycemia from quinine-induced hyperinsulinemia and parasite glucose consumption — check glucose q4h

— DIC, severe anemia, splenic rupture (especially P. vivax)

— Post-artesunate delayed hemolysis in 10–25% — weekly CBC ×4 weeks

— Dengue hemorrhagic fever / dengue shock syndrome during defervescence (days 3–7)

— Plasma leakage → pleural effusions, ascites, hemoconcentration

— Severe bleeding, hepatitis, myocarditis, encephalitis

— Second infection with different serotype = highest risk for severe disease (antibody-dependent enhancement)

— Intestinal perforation (terminal ileum) — surgical emergency

— GI hemorrhage

— Typhoid encephalopathy — indication for adjunctive dexamethasone

— Myocarditis, hepatitis, chronic carriage (gallbladder, esp. with cholelithiasis)

— Weil disease: jaundice, AKI, hemorrhage

— Pulmonary hemorrhage syndrome (high mortality)

— Myocarditis, aseptic meningitis

— Vasculitis → multi-organ failure if untreated

— RMSF mortality up to 20–30% without prompt doxycycline

— Rupture into pleural/pericardial/peritoneal space

— Chronic: portal hypertension, bladder cancer (S. haematobium), CNS schistosomiasis

— Jarisch-Herxheimer in leptospirosis/spirochete treatment

— C. diff from broad-spectrum antibiotics

CCS pearl: In severe malaria, check glucose every 4 hours and monitor CBC weekly for 4 weeks after artesunate — missing post-artesunate delayed hemolysis is a classic preventable error.

Severe malaria complications:

Dengue complications:

Typhoid complications (weeks 3–4 if untreated):

Leptospirosis:

Rickettsial:

Amebic liver abscess:

Schistosomiasis:

Treatment-related:

When to Escalate — ICU, Consultation, and Inpatient Triage

— Severe malaria (any WHO criterion)

— Dengue shock syndrome or DHF with hemodynamic instability

— Suspected VHF (with appropriate isolation)

— Septic shock from any source

— Cerebral involvement: cerebral malaria, Japanese encephalitis, meningococcus

— ARDS, AKI requiring CRRT, DIC

— Massive GI bleed or intestinal perforation from typhoid

— Infectious diseases: all severe malaria, suspected VHF, undifferentiated fever after initial workup, immunocompromised host

— Public health / state health department: suspected VHF, measles, novel respiratory pathogens, cholera, plague — mandatory reporting

— CDC Emergency Operations Center (770-488-7100): suspected VHF, unusual pathogens, artesunate access historically

— Surgery: typhoid perforation, amebic abscess rupture, splenic rupture

— OB/MFM: any pregnant febrile returnee

— Hematology: post-artesunate hemolysis, severe thrombocytopenia

— Unable to tolerate PO antimalarials

— P. falciparum infection (admit for first 24h to confirm response and rule out severity)

— Pregnancy

— Comorbidities (renal/hepatic disease, immunocompromise, age >65)

— Dengue with warning signs

— Suspected typhoid pending cultures

— Unreliable follow-up or social barriers

— Suspected VHF: single room, dedicated equipment, PPE per CDC algorithm, notify hospital epidemiology immediately

— Suspected TB or measles: airborne isolation, N95

— Cholera: contact precautions

— Community hospital without ID/ICU capability → transfer for confirmed severe malaria, VHF, or complex tropical disease

Step 3 management: A returning traveler from a current Ebola-affected region with fever must be placed in isolation immediately, then evaluated — calling public health before doing any lab draw is the correct sequence, both for patient care and for staff safety.

ICU admission criteria:

Mandatory specialty consultations:

Inpatient admission for clinically stable patients if:

Isolation triggers — act before testing returns:

Transfer considerations:

Key Differentials — Other Infectious Causes by Region

— Malaria (P. falciparum dominant) — always first

— African tick-bite fever (R. africae) — eschars, especially after safari

— Schistosomiasis (freshwater exposure — Lake Malawi classic)

— Typhoid

— VHF (Ebola, Lassa, Marburg) — depends on outbreak status

— African trypanosomiasis (tsetse fly, Winterbottom sign)

— Acute HIV

— Dengue — extremely common

— Enteric fever (XDR typhoid from Pakistan)

— Chikungunya

— Japanese encephalitis (rural rice paddies)

— Melioidosis (Burkholderia pseudomallei) — diabetics, Thailand, northern Australia

— Scrub typhus (Orientia tsutsugamushi)

— Leptospirosis

— Hepatitis A/E

— Dengue, Zika, chikungunya

— Malaria (Amazon basin, P. vivax common)

— Chagas disease (chronic, but acute reactivation possible)

— Leptospirosis (post-flooding, urban Brazil)

— Yellow fever (jungle and savanna)

— Bartonellosis (Andes)

— Cutaneous/visceral leishmaniasis

— MERS-CoV (camel exposure)

— Brucellosis (unpasteurized dairy)

— Q fever

— Crimean-Congo hemorrhagic fever

— Tick-borne relapsing fever

— Freshwater swimming → schistosomiasis, leptospirosis

— Caves → histoplasmosis, rabies (bats), Marburg

— Undercooked pork → trichinellosis, taenia

— Tick bite → rickettsial, tick-borne relapsing fever, Lyme (in endemic areas)

— Sexual exposure → acute HIV, hep B, syphilis, gonorrhea

— Hospitalization abroad → MDR organisms, surgical site infections

Key distinction: Melioidosis can mimic TB clinically (cavitary lung disease, chronic course) but causes acute fulminant sepsis in diabetics — culture is key (Burkholderia pseudomallei on routine media). Always inform the micro lab of travel exposure so they handle cultures with BSL-3 precautions.

Sub-Saharan Africa (the highest-yield region on exams):

South/Southeast Asia:

Latin America and Caribbean:

Middle East / Arabian Peninsula:

Specific exposure clues:

Key Differentials — Non-Infectious and Cosmopolitan Causes

— Community-acquired pneumonia (typical and atypical pathogens)

— UTI / pyelonephritis

— Influenza, RSV, COVID-19 — global circulation, often the actual diagnosis

— Acute viral syndromes (EBV, CMV, acute HIV)

— Streptococcal pharyngitis / peritonsillar abscess

— Cellulitis, abscess from insect bites or trauma abroad

— Antimalarial prophylaxis itself (mefloquine, atovaquone-proguanil less so)

— Antibiotics started for traveler's diarrhea

— Relative bradycardia, eosinophilia are clues

— Long-haul flights → DVT/PE can present with low-grade fever

— Often overlooked in returning travelers

— New-onset adult Still disease, reactive arthritis, vasculitis

— Flare of underlying lupus or IBD

— Lymphoma (B symptoms), leukemia

— Hepatocellular carcinoma in chronic HBV/HCV carriers

— Thyroid storm, adrenal crisis, pheochromocytoma — rare but classic distractors

— Sickle cell crisis, asthma exacerbation, decompensated heart failure

— Diagnosis of exclusion

Board pearl: A returning traveler with fever plus pleuritic chest pain, tachycardia, and hypoxia after a long-haul flight is a PE until proven otherwise — order CTPA, don't reflexively send malaria smears only. The trap on Step 3 is the exotic-sounding history pulling you away from the actual high-prevalence diagnosis.

Don't anchor on the tropics — common things stay common:

Drug fever:

Venous thromboembolism:

Inflammatory and rheumatologic:

Malignancy presenting during/after travel:

Endocrine and metabolic:

Heat-related illness or dehydration mimicking systemic infection

Pulmonary embolism in returning long-haul flyers — fever in ~14%

Acute appendicitis, cholecystitis, diverticulitis — coincidental but life-threatening if missed

Post-travel exacerbation of chronic disease:

Psychogenic / factitious fever:

Secondary Prevention, Discharge Planning, and Long-Term Care

— Confirm completion of full antimalarial course (most failures are incomplete therapy)

— Hypnozoite eradication for P. vivax/ovale: primaquine 14 days or tafenoquine single dose after G6PD testing

— Carriage eradication after typhoid: ciprofloxacin 4 weeks if susceptible, especially in food handlers and gallstone carriers; consider cholecystectomy in chronic carriers

— Luminal agent after amebic abscess (paromomycin or iodoquinol) to clear cysts

— Hepatitis A vaccine for unvaccinated travelers (and confirmed cases' contacts)

— Hepatitis B series if exposure risk

— Update typhoid vaccine if continued travel planned (only 50–80% effective, but useful)

— Yellow fever booster if appropriate (now considered lifelong for most)

— Tdap, MMR, varicella status check

— Discuss adherence-friendly prophylaxis (daily atovaquone-proguanil vs weekly mefloquine vs daily doxycycline)

— Insect-bite avoidance: DEET 20–30%, permethrin-treated clothing, bed nets

— Food and water precautions: "boil it, cook it, peel it, or forget it"

— Safe sex counseling and condom availability

— Avoiding freshwater swimming in schistosomiasis areas

— Pre-travel consultation 4–6 weeks before next trip

— HIV, HBV, HCV, syphilis

— Strongyloides serology

— Schistosoma serology

— TB screening (IGRA)

— Chagas serology (Latin America)

— Provide patient with diagnosis summary and treatment record for future providers and pre-travel clinics

Step 3 management: Any patient with P. vivax or P. ovale must have G6PD level checked and primaquine or tafenoquine prescribed before leaving the hospital — relapse from hypnozoites occurs weeks to months later and is a frequent Step 3 follow-up question.

Pre-discharge medication reconciliation:

Vaccinations indicated post-illness or post-travel:

Counseling for future travel:

Screening labs at follow-up (especially for migrants and long-term travelers):

Documentation:

Follow-Up, Monitoring, and Counseling Cadence

— Weekly CBC ×4 weeks after IV artesunate (post-artesunate delayed hemolysis)

— Repeat smear or RDT at days 3, 7, 28 to confirm clearance

— Symptom diary — any return of fever in 4 weeks = repeat smear

— P. vivax/ovale: counsel on relapse symptoms even after primaquine completion

— Outpatient recheck in 24–48h during febrile and defervescence phase

— CBC trend (Hct, platelets) until recovery

— Reinforce avoidance of NSAIDs for at least 1 week post-recovery

— Counsel on second-infection risk — different serotype = higher severe dengue risk

— Repeat stool culture at 1 and 3 months to detect chronic carriage (~3–5%)

— LFTs if hepatitis was present

— Counseling against food handling occupations until cleared

— Reassess at 1–2 weeks for symptom resolution

— Watch for long-term sequelae (rare neurologic deficits from severe RMSF)

— Renal and hepatic function recheck at 2 and 6 weeks

— Counsel on occupational re-exposure prevention

— Repeat egg studies or serology at 3 and 6 months

— Consider second praziquantel dose at 3 months

— TB follow-up screening at 8–10 weeks post-return if exposure risk (IGRA conversion)

— Sexual health: repeat HIV and syphilis at 6 weeks and 3 months if exposure occurred

— Mental health: travel-related PTSD, especially after VHF outbreak exposure or trauma

— Clear discharge summary to PCP including pathogen, treatment, pending labs, follow-up labs needed, and any reportable disease status

Board pearl: Recurrent fever 2–6 months after African travel in a patient who completed doxycycline prophylaxis is classic P. ovale or P. vivax relapse — the prophylaxis killed blood-stage parasites but not liver hypnozoites. Get a smear and check G6PD for radical cure.

Post-malaria follow-up:

Post-dengue follow-up:

Post-typhoid follow-up:

Post-rickettsial:

Post-leptospirosis:

Post-schistosomiasis:

General travel medicine follow-up themes:

Documentation for transitions of care:

Ethical, Legal, and Patient Safety Considerations

— Immediately reportable to local/state health and CDC: viral hemorrhagic fevers (Ebola, Lassa, Marburg, CCHF), plague, cholera, yellow fever, novel influenza, SARS/MERS, measles, anthrax, smallpox

— Routinely reportable: malaria, typhoid, hepatitis A/B/C, HIV, TB, brucellosis, leptospirosis, rabies exposure

— Failure to report can carry legal liability and clearly violates public health duty

— Public health authorities can impose quarantine for credible threats (TB, novel respiratory pathogens, VHF) — patient autonomy is overridden by community safety

— Document refusal of isolation and notify public health and hospital administration

— IV artesunate was previously investigational and required IND consent; now FDA-approved but still warrants discussion of post-artesunate hemolysis risk

— Primaquine in G6PD-deficient patients: hemolysis risk must be explicitly disclosed and G6PD tested before administration

— Live vaccine catch-up in immunocompromised needs careful risk discussion

— Acute HIV in a returning traveler triggers partner notification obligations through public health

— Many states have specific laws on disclosure of HIV status to sexual partners

— Patient discharged from ED with "viral syndrome" who actually has untreated falciparum malaria → high-mortality miss; document smear results and explicit follow-up plan, with safety-net return precautions

— Hand-off communication should explicitly note pending malaria smears, blood cultures, and serologies

— Needlestick from a returning traveler with possible HBV/HCV/HIV → standard PEP protocols apply

— Healthcare worker exposure to suspected VHF → immediate occupational health and public health notification

— VFR travelers (visiting friends and relatives) less likely to access pre-travel care due to cost and language — counsel on community resources

Step 3 management: When a returning traveler with confirmed measles is discharged, the physician must report to public health and ensure contact tracing for the ED waiting room and household — this is a non-negotiable patient-safety and public-health duty, not a courtesy.

Mandatory reportable diseases (US):

Isolation and personal liberty:

Informed consent edge cases:

Confidentiality vs partner notification:

Transitions of care risks:

Occupational exposures:

Travel medicine and equity:

High-Yield Associations and Rapid-Fire Clinical Facts

Board pearl: "Fever + eosinophilia in a returning traveler" should always prompt thinking of helminths (schistosoma, strongyloides, filaria, fasciola) — bacterial and viral infections cause eosinopenia, not eosinophilia.

Relative bradycardia (Faget sign): typhoid, yellow fever, brucellosis, leptospirosis, Legionella, drug fever

Eschar: African tick-bite fever, scrub typhus, Mediterranean spotted fever, anthrax

Rose spots: typhoid (blanching salmon macules on trunk)

Conjunctival suffusion: leptospirosis

Retro-orbital pain + saddleback fever: dengue

Polyarthritis persisting weeks: chikungunya

Cerebral malaria classic patient: child or non-immune adult from sub-Saharan Africa with falciparum, AMS, coma

Winterbottom sign: posterior cervical lymphadenopathy in African trypanosomiasis

Romaña sign: unilateral periorbital swelling in acute Chagas

Katayama fever: acute schistosomiasis with fever, urticaria, eosinophilia 4–8 weeks post-freshwater exposure

Snail-track stools (currant jelly): amebic dysentery

Anchovy-paste pus: amebic liver abscess on aspiration

Hemoglobinuria + severe malaria: "blackwater fever"

Post-artesunate delayed hemolysis: 10–25% incidence, weekly CBC ×4 weeks

Triad of meningococcemia: fever, petechial rash, hypotension; Waterhouse-Friderichsen if adrenal hemorrhage

Melioidosis: "Vietnamese time bomb" — diabetics, SE Asia/northern Australia, cavitary lung disease + sepsis

Q fever: unpasteurized dairy, sheep/goat exposure, endocarditis as chronic form

Trichinellosis: undercooked pork/bear, periorbital edema + eosinophilia + myalgia

Visceral leishmaniasis (kala-azar): massive splenomegaly, pancytopenia, hypergammaglobulinemia, India/Africa

Loa loa: subconjunctival migration of worm, calabar swellings

Strongyloides hyperinfection: post-steroid use, gram-negative meningitis from gut translocation

Chagas reactivation: in HIV/transplant patients from Latin America

G6PD must be tested before: primaquine, tafenoquine, dapsone, rasburicase

Doxycycline now AAP-endorsed for serious rickettsial disease in children of any age

XDR typhoid from Pakistan: azithromycin or carbapenem only

Board Question Stem Patterns

— "A 32-year-old returns from Nigeria 10 days ago, took no prophylaxis. Temp 39.5°C, jaundice, parasitemia 8%, schizonts on smear, creatinine 2.5."

— Answer: IV artesunate, ICU admission, severe malaria management

— "Patient returned from India 4 months ago, treated with chloroquine, now febrile again. Smear shows ring forms with Schüffner dots."

— Answer: Check G6PD, then primaquine for hypnozoite eradication

— "Returned from Thailand 5 days ago, fever now defervescing, but increasing abdominal pain, Hct rising, platelets 40,000."

— Answer: Admit, IV fluids, avoid NSAIDs — dengue warning signs/DHF

— "Returned from Pakistan 2 weeks ago, week-long fever stepwise rising, abdominal pain, rose spots, splenomegaly, relative bradycardia."

— Answer: Blood cultures + empiric ceftriaxone (XDR concern); azithromycin alternative

— "Returned from South African safari, fever, headache, black eschar at ankle, regional adenopathy."

— Answer: Doxycycline empirically — African tick-bite fever

— "Triathlete who swam in flooded river in Hawaii or Costa Rica, fever, conjunctival suffusion, calf pain, AKI, jaundice."

— Answer: IV penicillin or ceftriaxone; doxycycline if mild

— "Mexico travel, fever + RUQ pain, single right-lobe liver lesion, no biliary dilation, eosinophilia absent."

— Answer: Metronidazole + luminal agent (paromomycin)

— "Lake Malawi swim 6 weeks ago, fever, urticaria, eosinophilia, hepatomegaly, negative stool O&P."

— Answer: Serology + steroids + praziquantel at 6–8 weeks

— "Returned from Cancun, fever, pleuritic chest pain, tachycardia, hypoxia after 8h flight."

— Answer: CTPA for PE, not malaria smear

— "Mediterranean patient with P. vivax given primaquine, develops back pain and dark urine."

— Answer: G6PD-mediated hemolysis — should have been screened first

Key distinction: Step 3 stems frequently embed the management cascade (smear → severity assessment → drug choice → follow-up labs) rather than asking just for the diagnosis. Know the entire pathway, not just the bug.

Classic falciparum stem:

Vivax relapse stem:

Dengue stem:

Typhoid stem:

Rickettsial stem:

Leptospirosis stem:

Amebic liver abscess stem:

Schistosomiasis stem:

Pitfall stem (anchoring):

G6PD pitfall:

One-Line Recap

The returning febrile traveler is malaria-until-proven-otherwise from Africa, dengue-until-proven-otherwise from Southeast Asia and Latin America, and a "common things stay common" cosmopolitan infection everywhere else — workup is anchored by thick/thin smears with RDT, blood cultures, CBC with differential, CMP, UA, HIV, pregnancy test, and CXR, while empiric therapy targets the most lethal plausible pathogen based on incubation period and exposure.

Board pearl: The single most common preventable death in returning travelers is delayed diagnosis of falciparum malaria — when in doubt, draw the smear, call ID, and start IV artesunate.

Rule out malaria first in any febrile returnee with possible endemic exposure — single negative smear is never enough; repeat q12–24h ×3, and treat severe disease with IV artesunate before confirmation if clinically warranted.

Tailor empiric therapy by syndrome: doxycycline for rickettsial, ceftriaxone for enteric fever/sepsis, supportive care + careful fluids for dengue, IV penicillin/ceftriaxone for severe leptospirosis, metronidazole + luminal agent for amebic liver abscess.

Special-population landmines: check G6PD before primaquine/tafenoquine, admit all pregnant patients with malaria, monitor weekly CBC ×4 weeks after artesunate, screen for strongyloides before any steroid course in prior tropical residents.

Public health duty is non-negotiable: isolate and report suspected VHF, measles, typhoid, malaria, and TB; document follow-up plans for pending smears and cultures; arrange radical cure for P. vivax/ovale before discharge; and reinforce future-travel pre-travel consultation, prophylaxis adherence, vector avoidance, and food/water precautions.