Infectious disease
Fever in an adult
Acute febrile illness with or without an obvious source
Time-critical presentation5-stage reasoningCase walk-through
What to ask
Find the source, then decide how sick the patient is — in that order, but at the same speed.- Duration and pattern of fever, and localising symptoms in every system.
- Travel with dates, mosquito and freshwater exposure, animal contact, sick contacts, sexual history.
- Immunosuppression, chemotherapy timing, splenectomy, indwelling devices, recent surgery or instrumentation.
- Antibiotics already taken, and drugs that cause fever.
- Vaccination status and prophylaxis taken during travel.
Discriminators
- Fever within 21 days of travel to an endemic area makes malaria a must-exclude.
- Fever within 6 weeks of chemotherapy is neutropenic sepsis until the count says otherwise.
- Fever with a non-blanching rash is meningococcal disease until proven otherwise.
Case walk-through — Day 4 fever that just broke
5 decisions · moderateCase vignette
A 24-year-old woman living in an endemic city has had 4 days of high fever, severe myalgia and retro-orbital pain. Today she is afebrile but has severe abdominal pain and repeated vomiting. Blood pressure 110/95 mmHg, pulse 108/min, platelets 55 × 10⁹/L, haematocrit risen from 38% to 47%.
- 1
How do you interpret today's change?
- 2
Blood pressure is 110/95 mmHg with a pulse of 108. What does the pulse pressure tell you?
Answer the previous step to continue.
- 3
Which fluid strategy is correct?
Answer the previous step to continue.
- 4
Her platelets fall to 22 × 10⁹/L with no bleeding. What do you do?
Answer the previous step to continue.
- 5
Forty-eight hours later she is stable with improving appetite, but now has bibasal crackles and mild breathlessness on the current fluid rate. What is happening?
Answer the previous step to continue.
Full checklist
Original structured checklist- 1
History
- Duration and pattern of fever; localising symptoms by system
- Travel, mosquito and freshwater exposure, animal contact, sick contacts
- Immunosuppression, chemotherapy, splenectomy, indwelling devices, recent surgery
- Medications including recent antibiotics and drugs causing fever
- 2
Examination
- Full vital signs including capillary refill and mental state
- Head-to-toe source search: skin, lines, joints, perineum, feet, teeth
- Rash character; meningism; new murmurs; abdominal tenderness
- Look specifically for an eschar, jaundice or conjunctival suffusion in travellers
- 3
Initial tests
- Blood cultures before antibiotics (two sets), lactate, FBC, CRP, renal and liver profile
- Urinalysis and culture, chest radiograph, malaria smear or rapid test in travellers
- Dengue NS1 or IgM by day of illness; leptospira and scrub typhus serology as indicated
- Targeted imaging or lumbar puncture where clinically indicated
- 4
Differential
- Bacterial: pneumonia, urinary, skin and soft tissue, intra-abdominal, endocarditis, meningitis
- Viral: influenza, COVID-19, dengue, HIV seroconversion, EBV
- Tropical and zoonotic: malaria, enteric fever, leptospirosis, scrub typhus
- Non-infective: venous thromboembolism, malignancy, drug fever, inflammatory disease
- 5
Immediate treatment
- If sepsis criteria are met: broad-spectrum antibiotics within 1 hour, cultures, 30 mL/kg crystalloid for hypoperfusion, lactate remeasurement
- Neutropenic fever: empirical antipseudomonal beta-lactam immediately, do not wait for the count
- Suspected meningococcal disease: antibiotics before transfer and before lumbar puncture
- Source control: drainage, line removal, debridement
- Antipyretics for comfort; paracetamol only if dengue is possible
- 6
Follow-up
- Review microbiology at 48-72 hours and de-escalate or stop antibiotics
- Reconsider the diagnosis if there is no response by 72 hours
- Notify public health for notifiable diseases and complete contact tracing
Related diseases
Demo content. Educational decision support only. Verify every dose, citation and recommendation against your national formulary and the primary source before clinical use.