Fever in adults
Who is the patient and where is the source? In a Pakistani ER, dengue, malaria and typhoid are on the list for every fever.
A 28-year-old man has had fever for 4 days with body aches and headache. Temperature 39.4 °C, pulse 104, BP 112/70. No cough, no rash, no neck stiffness. Platelets 96,000/µL. He wants "a drip and an injection" so he can go home.
What do you check before you decide?
- Sepsis firstLow BP, fast breathing, confusion, mottled skin, low urine: start the sepsis pathway.
- Is this a high-risk patient?Neutropenic, pregnant, elderly, diabetic, on steroids, no spleen.
- Day of illnessDecides which dengue and typhoid tests make sense.
- Hunt the sourceChest, urine, skin, abdomen, meninges, joints, lines, heart murmur.
- Tests for the local threeDengue (NS1 or IgM), malaria (RDT or smear), typhoid (blood culture).
- Paracetamol, not NSAIDsNSAIDs are unsafe if this could be dengue.
- Safety-net if dischargedWarning signs in writing, return date, who to call.
- Low BP or lactate above 2 mmol/L (18 mg/dL)
- Confusion, neck stiffness or a fit
- Neutropenic fever
- Dengue warning signs
- Pregnant with fever
- Jaundice with fever and confusion
- Meningitis
- Severe malaria (falciparum)
- Dengue shock
- Infective endocarditis (new murmur, IV drug use)
- Liver abscess
- TB
- Heat stroke
| Fever | Temperature 38 °C or above |
| Hypothermia in sepsis | Below 36 °C is also a red flag |
| Neutropenic fever | Neutrophils below 500/µL with fever: antibiotics within 1 hour |
| Dengue critical phase | Usually days 3–7, as the fever settles |
| Platelets in dengue | Watch the trend and the haematocrit, not one number |
| Paracetamol, adult | Maximum 4 g in 24 hours (less if under 50 kg or liver disease) |
Check every dose against a current drug reference and your hospital protocol.
On this page
Is this sepsis?
Any one of these: systolic BP below 90, RR 22 or more, new confusion, lactate above 2 mmol/L, little or no urine, mottled or cold skin. Start the sepsis pathway: cultures, antibiotics, fluids, lactate, within the hour.
Which tests on which day?
- Day 1–5Dengue NS1 antigen (best early); malaria RDT or smear
- Day 1–7Typhoid blood culture (before antibiotics)
- Day 5 onwardDengue IgM; NS1 may be negative now
- Day 7 onwardWidal is unreliable; do not diagnose typhoid on it alone
- Malaria: test every febrile patient in an endemic area or with travel. One negative smear does not exclude it: repeat in 12–24 hours if suspicion is high.
- Dengue: CBC daily. A rising haematocrit with falling platelets is the warning. See dengue.
- Typhoid: blood culture is the test; resistance patterns matter in Pakistan (XDR typhoid). See enteric fever.
Find the source
Meningitis or meningococcal sepsis: antibiotics now, see the meningitis guide
- Pneumonia
- TB if long cough, weight loss
- Cholangitis
- liver abscess
- hepatitis
- Dengue
- malaria
- typhoid
- endocarditis
- TB
- drug fever
High-risk groups
| Patient | Why it matters | What to do |
|---|---|---|
| On chemotherapy | Neutropenic sepsis can kill within hours | Antibiotics within 1 hour without waiting for the count, per hospital policy |
| Pregnant | Sepsis, pyelonephritis, malaria worse in pregnancy | Obstetric review; check fetal well-being |
| Elderly | May not mount a fever; confusion may be the only sign | Low threshold for admission |
| Diabetic | Hidden infections: foot, kidney, skin | Check sugar and ketones |
| On steroids or immunosuppressed | Signs blunted | Treat as high risk |
Treatment
- No NSAIDs (diclofenac, ibuprofen) if dengue is possible: bleeding risk.
- No antibiotics "to cover" a well patient with a viral-pattern fever and no focus. They mask typhoid cultures and drive resistance.
- Unwell with no source: take cultures, then follow the hospital's empirical sepsis policy.
Discharge or admit?
| Can go home if | Admit if |
|---|---|
| Haemodynamically normal, eating and drinking | Any sepsis criteria |
| Reliable follow-up within 24–48 hours | Dengue warning signs or rising haematocrit |
| No high-risk features | Malaria positive (falciparum) or severe malaria features |
| Clear written warning signs | Neutropenic, pregnant, elderly and unwell |
Warning signs to write down for dengue: abdominal pain, persistent vomiting, bleeding, drowsiness or restlessness, cold hands and feet, passing little urine, feeling worse as the fever settles.
Frequently asked questions
What causes fever in adults in Pakistan?
Viral fevers, dengue, malaria, typhoid, urinary infection, pneumonia and TB are common. Always think of meningitis and sepsis in an unwell patient.
What is the best treatment for fever?
Treat the cause. For comfort, paracetamol is safest; avoid NSAIDs if dengue is possible.
What does fever with rigors mean?
Rigors suggest bacteraemia (pyelonephritis, cholangitis, pneumonia) or malaria. Take blood cultures and a malaria test.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A patient is on day 2 of fever and dengue is suspected. Which test is best?
Answer: Dengue NS1 antigen. NS1 is best in the first 5 days; IgM becomes positive from about day 5.
- Blood culture: Not for dengue.
- Widal: Not for dengue.
- Dengue IgG: Indicates past infection.
- Dengue IgM: Usually negative this early.
2. A dengue patient on day 5 has platelets falling from 140,000 to 85,000/µL and haematocrit rising from 40 to 47%. What does this mean?
Answer: Plasma leakage. A rising haematocrit with falling platelets signals plasma leakage. Admit and follow the dengue fluid plan.
- Bleeding: Haematocrit would fall.
- Normal viral fever: Not with this trend.
- Recovery: Rising haematocrit means leak.
- Lab error: Act on it.
3. A patient with fever might have dengue. Which drug for fever should be avoided?
Answer: Diclofenac. NSAIDs increase bleeding risk in dengue. Use paracetamol only.
- Tepid sponging: Fine.
- Paracetamol: Safe at correct dose.
- Oral rehydration solution: Safe.
- Ondansetron: Not contraindicated.
4. A 25-year-old with cerebral falciparum malaria is being treated with IV artesunate. He has a further seizure. Which bedside test should be checked first?
Answer: Capillary blood glucose. Hypoglycaemia is a common, treatable complication of severe falciparum malaria (parasite glucose consumption, impaired gluconeogenesis, quinine-induced insulin release; pregnancy and children at higher risk). It can mimic or worsen cerebral malaria; check glucose frequently and treat with IV dextrose. Other complications: acidosis, AKI, severe anaemia, pulmonary oedema/ARDS, shock (algid malaria), DIC, haemoglobinuria (blackwater fever).
- Peripheral blood film count: Parasite count is not the immediate priority.
- Serum amylase: Amylase is irrelevant here.
- Troponin: Troponin is irrelevant here.
5. A woman with SLE and antiphospholipid antibodies has small sterile vegetations on both surfaces of the mitral valve on echo. What is this called?
Answer: Libman–Sacks endocarditis. Libman–Sacks endocarditis is non-bacterial verrucous endocarditis in SLE (especially with antiphospholipid syndrome): small sterile vegetations on both sides of the valve leaflets (mitral commonest). Can embolise or cause regurgitation. Non-bacterial thrombotic (marantic) endocarditis occurs in malignancy and hypercoagulable states. Rheumatic vegetations sit along closure lines.
- Infective endocarditis: The vegetations are sterile, not infective.
- Rheumatic carditis: Rheumatic carditis has a different history.
- Marantic endocarditis of cancer: Marantic endocarditis is linked with malignancy.
6. Which part of the brain directly controls autonomic reflexes and body temperature?
Answer: Hypothalamus. The hypothalamus integrates autonomic control: temperature, hunger, thirst, water balance (ADH), circadian rhythms and pituitary function. It acts through brainstem autonomic centres and the pituitary.
- Thalamus: A sensory relay station.
- Cerebral cortex: Higher functions; it can influence but does not directly control autonomic reflexes.
- Cerebellum: Coordinates movement.
- Basal ganglia: Control movement initiation.
7. At the start of a fever, the hypothalamic set point rises. What does the body do?
Answer: Vasoconstriction and shivering. Pyrogens (IL-1, IL-6, TNF) trigger prostaglandin E2 in the hypothalamus, raising the set point. The body now 'feels cold', so it constricts skin vessels and shivers until temperature reaches the new set point. When the fever breaks, vessels dilate and sweating starts. Paracetamol and NSAIDs block PGE2 production.
- Heavy sweating: Happens when fever breaks.
- Skin vasodilatation: Happens when fever breaks.
- Stopping heat production: Heat production increases.
- Lowering the metabolic rate: Metabolic rate rises.
References and dose sources
- WHO guidelines for malaria
- WHO dengue guidelines for diagnosis, treatment, prevention and control
- NICE NG51: Sepsis
- NICE CG151 — neutropenic sepsis
- British Infection Association malaria guidance
- NICE NG240
- NICE NG253 — suspected sepsis in over 16s
- UKHSA — malaria guidance
- Paracetamol dosing: Drugs.com: Acetaminophen (paracetamol) dosage (see also our paracetamol dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.