Key Facts

Pyrexia in a returning traveller is a medical emergency until malaria is excluded. A systematic approach considering incubation period, geographic exposure, and clinical features is essential.

Epidemiology

• UK: ~1,500 imported malaria cases/year; ~5–10 deaths (mostly P. falciparum)
• Dengue: ~800 confirmed cases/year in England (imported)
• Enteric fever: ~500 cases/year (mainly travel to Indian subcontinent)
• Schistosomiasis: freshwater exposure in Africa

Aetiology by Incubation Period

Short (<10 days): dengue, chikungunya, Zika, rickettsial, enteric bacteria, VHF Medium (10–21 days): malaria, typhoid, hepatitis A, leptospirosis, acute HIV Long (>21 days): malaria (P. vivax/ovale), TB, hepatitis B, visceral leishmaniasis, amoebic liver abscess

Pathophysiology

• Malaria: Plasmodium parasites invade erythrocytes → haemolysis, cytokine storm, endothelial activation → microvascular obstruction (cerebral malaria)
• Dengue: antibody-dependent enhancement in secondary infection → vascular leak → dengue haemorrhagic fever
• Typhoid: Salmonella typhi invades Peyer's patches → bacteraemia → systemic infection

Key History

• Destination: sub-Saharan Africa (malaria, VHF), South/Southeast Asia (dengue, typhoid), South America
• Timing: date of return, onset of fever relative to travel
• Activities: freshwater exposure (schistosomiasis), animal contact (rabies, Q fever), unprotected sex (HIV, hepatitis B)
• Prophylaxis: malaria chemoprophylaxis compliance, vaccinations received
• Insect bites: mosquitoes, ticks

Presentations by Diagnosis

• Malaria: paroxysmal fever/rigors, headache, myalgia, splenomegaly, jaundice
• Dengue: high fever, severe headache/retro-orbital pain, myalgia/arthralgia, rash, thrombocytopenia
• Typhoid: insidious high fever, relative bradycardia, rose spots (2–4mm salmon-pink macules on trunk), constipation then diarrhoea
• Hepatitis A: jaundice, nausea, RUQ pain, markedly raised ALT

Red Flags

• Malaria parasitaemia >2% (severe malaria)
• Haemorrhagic features (VHF, severe dengue)
• Altered consciousness (cerebral malaria, meningitis)
• Jaundice + fever (malaria, hepatitis, leptospirosis)

Immediate (All Febrile Returning Travellers)

• Thick and thin blood films for malaria - ×3 over 24–48h; DO NOT wait for cyclical fever
• Malaria rapid diagnostic test (RDT): adjunct but does not replace films
• FBC: thrombocytopenia (dengue, malaria), eosinophilia (schistosomiasis, helminths)
• U&Es, LFTs: organ involvement, hepatitis
• CRP: degree of inflammation
• Blood cultures: typhoid, bacteraemia
• HIV test: always include

Directed Investigations

• Dengue NS1 + serology: if travel to endemic area within 14 days
• Hepatitis A/B/C serology: if jaundice or raised LFTs
• Stool MC&S + ova/parasites: if diarrhoea
• Schistosoma serology: if freshwater exposure + eosinophilia (test at ≥12 weeks post-exposure)
• CXR: if respiratory symptoms (TB, PCP)
• Urinalysis: schistosomiasis (haematuria)

VHF Risk Assessment

• PHE algorithm: travel to VHF-endemic area + fever within 21 days → risk assessment → if high risk: IMMEDIATE ISOLATION, contact PHE

Malaria (P. falciparum)

Uncomplicated (parasitaemia <2%, no severity criteria):

• Artemisinin-based combination therapy (ACT): artemether-lumefantrine (Riamet) for 3 days
• Or atovaquone-proguanil (Malarone) for 3 days

Severe malaria (parasitaemia ≥2%, organ dysfunction, cerebral):

• IV artesunate 2.4mg/kg at 0, 12, 24 hours then daily until oral tolerated
• HDU/ICU admission; exchange transfusion if parasitaemia >30%

P. vivax/ovale:

• ACT or chloroquine for 3 days
• PLUS primaquine 15mg OD for 14 days (radical cure - eliminates hypnozoites); check G6PD first

Dengue

• Supportive: fluids, paracetamol (AVOID NSAIDs/aspirin - bleeding risk)
• Monitor for dengue haemorrhagic fever/shock syndrome
• No specific antiviral

Typhoid

• Azithromycin 500mg OD for 7 days (uncomplicated)
• IV ceftriaxone 2g OD if severe or quinolone-resistant
• Stool cultures after treatment to confirm clearance

VHF

• Strict isolation, full PPE, contact PHE
• Supportive care; ribavirin for Lassa fever

Referral Criteria

• All suspected malaria: immediate assessment (same-day malaria films)
• Infectious diseases: complex/severe cases
• PHE: VHF risk, notifiable diseases
• ICU: severe malaria, dengue shock syndrome

• Uncomplicated P. falciparum: excellent with prompt treatment (mortality <0.1%)
• Severe P. falciparum: mortality 10–20% even with treatment
• Dengue: mortality <1% with supportive care; dengue shock syndrome mortality up to 20% without treatment
• Typhoid: <1% mortality with antibiotics; complications include intestinal perforation
• Delay in diagnosis is the major risk factor for poor outcome in malaria

Causes of Fever by Incubation Period

Severe Malaria Criteria (WHO)