01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Returning-traveller fever combines ordinary UK infections with imported disease. Geography changes prior probability but never replaces assessment for pneumonia, pyelonephritis, COVID-19, endocarditis or drug reaction. The safest sequence is ABCDE, transmission risk, malaria exclusion, exposure-incubation timeline, syndrome examination and targeted sampling.
Malaria testing is urgent and may need repetition when initial microscopy or rapid testing is negative but suspicion remains. Severe malaria can cause confusion, acidosis, hypoglycaemia, jaundice, renal injury and respiratory distress. Early specialist advice is essential because treatment and level of care depend on species, parasitaemia and organ involvement.
High-consequence infections are uncommon but operationally important. Recent outbreak information, country, healthcare exposure, animal contact, bleeding and severe respiratory illness determine isolation and referral. Staff should use the designated pathway rather than collecting unplanned specimens that might expose laboratory personnel.
Key points
- Ask exactly where and when the patient travelled, including stopovers, urban versus rural setting, dates, season and illness onset; incubation time removes many impossible diagnoses.
- Malaria is the first exclusion after travel to a risk area because falciparum disease can deteriorate rapidly and prophylaxis does not provide complete protection.
- Take a precise exposure history: mosquitoes and ticks, fresh water, animals, food and water, sexual contact, healthcare, caves, funerals, mass gatherings and sick contacts.
- Use early isolation for possible airborne or high-consequence infection before an exhaustive interview; protect staff while urgent clinical care continues.
- Look for syndrome patterns—rash, jaundice, diarrhoea, eosinophilia, cytopenias, hepatosplenomegaly, neurological change and respiratory failure—without treating any single clue as diagnostic.
- Discuss unusual samples and empirical treatment with infection or microbiology specialists; malaria films, cultures and molecular tests have timing and handling requirements.
- Notify suspected notifiable disease on clinical suspicion and coordinate contacts or post-exposure action through the local health-protection team.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Vector-borne infection
Malaria, dengue, chikungunya, rickettsial disease and other infections follow mosquito or tick exposure, with geography and incubation narrowing likelihood.
Food and water exposure
Enteric fever, hepatitis A or E and bacterial or protozoal gastrointestinal infections arise from contaminated food, water or sanitation failures.
Animal and environmental contact
Fresh water, livestock, wildlife, caves, soil and arthropods create risks including schistosomiasis, leptospirosis, brucellosis and fungal infection.
Human and healthcare exposure
Sexual contact, medical procedures, mass gatherings, sick contacts and funerals may transmit blood-borne, respiratory or high-consequence infections.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Pathogen entry
Organisms enter through skin, vectors, respiratory mucosa, gastrointestinal tract or blood and establish local or systemic infection.
- 2Bloodstream dissemination
Malaria parasites, bacteria, viruses or fungi spread through blood, producing fever and multi-organ manifestations beyond the entry site.
- 3Host inflammatory response
Innate immune cytokines reset temperature and alter endothelium, coagulation and perfusion; an excessive response can cause shock and organ injury.
- 4Organ-specific tropism
Different pathogens preferentially affect erythrocytes, liver, endothelium, marrow, nervous system or lung, creating the discriminating syndrome pattern.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Fever with rigors, headache, cytopenia, jaundice, confusion, acidosis or renal injury after malaria-area travel is an emergency even without a regular fever pattern.
Sustained fever, abdominal symptoms, relative bradycardia, hepatosplenomegaly or travel with unsafe food and water raises typhoid or paratyphoid disease.
Acute fever with rash, severe myalgia, arthralgia, retro-orbital pain, leucopenia or thrombocytopenia suggests dengue, chikungunya or another vector-borne virus according to geography.
Bleeding, unexplained shock, severe respiratory syndrome or exposure to outbreaks, healthcare, caves, animals or funerals requires immediate isolation and specialist risk assessment.
Focal urinary, respiratory, cardiac or skin findings may reveal an ordinary infection acquired before, during or after travel and should remain in the differential.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Urgent malaria blood films and rapid diagnostic testingFirst step - Why
- Detect malaria species, parasitaemia and features requiring severe-disease management.
- Interpretation and limitations
- A negative first test does not always exclude low parasitaemia. Repeat according to specialist and laboratory guidance when suspicion persists, and never wait for cyclical fever.
- 02
FBC, blood film, renal, liver, glucose, CRP and blood gas - Why
- Identify cytopenia, organ dysfunction, hypoglycaemia, eosinophilia and severity.
- Interpretation and limitations
- Thrombocytopenia occurs in malaria and dengue but is not specific. Eosinophilia suggests selected parasitic or drug causes and is often absent early.
- 03
Blood cultures before antibiotics - Why
- Detect enteric fever, bacteraemia and endovascular infection while preserving susceptibility yield.
- Interpretation and limitations
- Tell the laboratory the travel and antimicrobial history. Prior antibiotics reduce sensitivity, and resistant enteric organisms may require reference testing.
- 04
Syndrome-directed molecular or serological tests - Why
- Investigate arboviruses, respiratory viruses, HIV and other infections using the correct illness window.
- Interpretation and limitations
- PCR and antibody yield change with time from onset. Cross-reactive serology and past exposure require infection-specialist interpretation.
- 05
Imaging and targeted source samples - Why
- Assess pneumonia, abscess, hepatobiliary disease, neurological infection or another focal source.
- Interpretation and limitations
- Choose imaging from clinical findings and stability. Discuss hazardous or unusual specimens with microbiology before collection and transport.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Common UK infection
Pneumonia, pyelonephritis, COVID-19 and skin infection remain frequent and may be unrelated to the itinerary despite compelling travel history.
Malaria
Any fever after malaria-area travel requires urgent blood testing because early symptoms are non-specific and prophylaxis does not exclude disease.
Enteric or arboviral infection
Food, vector, incubation and laboratory patterns separate typhoid or paratyphoid disease from dengue and other acute viral syndromes.
Non-infectious disease
Pulmonary embolism, drug fever, inflammatory disease and malignancy can begin around travel and require ordinary probability-led assessment.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Travel from malaria regionExclude malaria immediatelyFirst stepAny current or recent fever follows travel to an area with malaria transmission.+
- 1Perform ABCDE, check glucose and travel dates, take urgent malaria films and rapid testing and request infection or tropical-medicine advice.
- 2Assess severity including consciousness, lactate or acidosis, renal function, jaundice, anaemia, respiratory compromise and parasitaemia; admit and treat promptly when severe or falciparum malaria is possible.
- 3Repeat testing when advised if the first result is negative and suspicion remains, while investigating other imported and ordinary infections in parallel.
02Possible high-consequence diseaseProtect staff and contacts earlyExposure and syndrome raise concern about a nationally designated high-consequence infection.+
- 1Place the patient in appropriate isolation, restrict non-essential contact, use designated PPE and call the local infectious-disease and health-protection pathway immediately.
- 2Continue emergency care using trained staff, record exposure details and avoid sending unannounced specimens through routine laboratory routes.
- 3Follow specialist instructions for transfer, sampling, notification, staff exposure and environmental control while maintaining confidentiality.
03Stable undifferentiated feverUse incubation and exposure to focus testsThe traveller is physiologically stable and immediate malaria and high-consequence pathways have been addressed.+
- 1Construct a country-by-date timeline and map food, water, vector, animal, freshwater, sexual, healthcare and medicine exposures against illness onset.
- 2Examine for rash, nodes, jaundice, organomegaly, murmur, focal chest, abdominal or neurological signs and obtain targeted cultures and laboratory tests.
- 3Review results with infection specialists, give syndrome-directed treatment when supported and provide explicit deterioration and pending-result follow-up.
Key medicines and prescribing safety2 treatments · regimens, roles and cautions+
Intravenous artesunate
Give 2.4 mg/kg intravenously at 0, 12 and 24 hours, then every 24 hours until oral treatment is tolerated; after at least three doses, complete a full specialist-selected oral combination course.Do not delay for transfer or perfect species confirmation when severe malaria is likely. Monitor glucose, parasitaemia and organ failure; arrange full blood count and haemolysis surveillance after discharge because delayed artesunate-associated haemolysis can emerge over the following 4 weeks.
Atovaquone with proguanil
For adults over 40 kg with selected uncomplicated falciparum malaria, give four 250/100 mg tablets orally once daily for three days with food.Not for severe malaria. Give with food, repeat a dose vomited within 1 hour, and seek an alternative after repeated vomiting. Review severe renal impairment, pregnancy and anticoagulant monitoring, avoid reusing a failed prophylactic drug, and confirm species-specific follow-up with the specialist service.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Severe malaria
Parasite burden and microvascular sequestration can cause coma, acidosis, hypoglycaemia, anaemia, kidney injury and respiratory failure.
Shock and organ failure
Enteric, rickettsial, leptospiral and viral infections can produce capillary leak, myocarditis, hepatitis, renal injury or coagulopathy.
Transmission to contacts
Airborne, faecal-oral, sexual and vector-associated pathogens may require isolation, contact tracing, prophylaxis, vaccination or coordinated environmental action through health-protection teams.
Delayed diagnosis
Failure to obtain exact geography, incubation and exposure can postpone effective therapy and allow avoidable clinical deterioration.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Repeat observations, consciousness, glucose, urine output, lactate and organ tests frequently in any unwell traveller because deterioration can be abrupt.
- For malaria, document species, parasitaemia and clearance according to specialist protocol and arrange follow-up for delayed artesunate-associated haemolysis.
- Track blood cultures, reference-laboratory tests and serology that may return after discharge, with named responsibility and a reliable contact route.
- Review isolation and contact actions with health protection as diagnosis and infectious period become clearer.
- Revisit the travel timeline when tests are negative; an incorrect country, date or exposure assumption can misdirect the entire investigation.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Prophylaxis does not exclude malaria
Adherence, absorption, resistance and imperfect efficacy mean a traveller can develop malaria despite taking preventive medicines.
Incubation is a diagnostic test
A disease cannot explain symptoms beginning outside its biological incubation range, so exact travel and onset dates have high discriminating value.
Ordinary infections remain common
A dramatic itinerary can distract from urinary infection, pneumonia, COVID-19 or endocarditis that requires the same evidence-led assessment as at home.
Phone before the specimen
For possible hazardous infections, advance laboratory and specialist communication protects staff and ensures the correct container, route and reference test.
11Common pitfallsFrequent interpretation and management errors.
- 01
Excluding malaria because prophylaxis was reportedly completed.
- 02
Waiting for a textbook fever cycle before ordering malaria films.
- 03
Collecting hazardous specimens before notifying the laboratory.
- 04
Ordering a broad travel serology panel without using timing and exposure.
- 05
Attributing all illness to travel and missing a common local infection.