The Febrile Child: Assessment and Initial Management

Introduction

Fever is defined as a body temperature of 38°C or above. It is the single commonest reason a child under 5 is brought to medical attention in the UK, accounting for a large share of GP consultations and around a fifth of paediatric emergency department attendances.¹

The overwhelming majority of these children have a self-limiting viral illness. A small minority have a serious bacterial infection - pneumonia, urinary tract infection, bacterial meningitis, septic arthritis, osteomyelitis or bacteraemia - and a smaller minority again are septic and deteriorating. The clinical problem is that in the first hours these children can look very similar, and the febrile child who dies usually looked reasonably well to somebody a few hours earlier.

This is why the assessment is structured rather than intuitive. NICE guideline NG143 provides a traffic light system that turns a set of soft impressions into a documented risk category with a defined action attached to each.¹ It is not a diagnostic tool - it does not tell you what the child has - but a triage tool that tells you what to do next and how quickly.

Two facts should shape your approach from the outset. First, the height of the temperature correlates poorly with the risk of serious illness above the age of 6 months; a child with 39.5°C who is playing is far less concerning than a child with 38.2°C who is mottled and unrousable. Second, response to antipyretics has no diagnostic value: children with meningococcal sepsis often perk up briefly after paracetamol, and this has misled many clinicians.

Measuring the temperature

How the temperature was taken matters, because different routes give systematically different readings, and because parental report of a fever is accepted as valid even when the child is afebrile in clinic.¹

Causes

Aetiology varies with age, immunisation status and season, but the broad distribution is consistent.

Viral - the large majority

• Upper respiratory tract infection, including otitis media and pharyngitis
• Bronchiolitis, most often respiratory syncytial virus, in infants under 1
• Croup, usually from parainfluenza virus
• Viral exanthems - measles, rubella, parvovirus B19, human herpesvirus 6 and the enteroviruses
• Influenza, adenovirus, SARS-CoV-2 and the common gastroenteritis viruses

Bacterial

• Urinary tract infection - the commonest serious bacterial infection in young children and the one most often missed, because there are no urinary symptoms in infancy
• Pneumonia - Streptococcus pneumoniae most commonly
• Bacterial meningitis and meningococcal septicaemia - much rarer since conjugate vaccination, but still the diagnosis that kills
• Septic arthritis and osteomyelitis - suspect in a child who will not weight bear or has a limb they refuse to use
• Group A streptococcal infection - scarlet fever, tonsillitis, and occasionally invasive disease
• Neonatal sepsis - group B Streptococcus, Escherichia coli and Listeria monocytogenes in the first weeks of life

Non-infective and other

• Kawasaki disease - consider in any child with fever for 5 days or more
• Malaria and imported infection - always take a travel history, as falciparum malaria can present as undifferentiated fever with no localising signs
• Juvenile idiopathic arthritis, particularly the systemic-onset form
• Malignancy, especially leukaemia
• Inflammatory bowel disease and the periodic fever syndromes in recurrent presentations
• Post-immunisation fever - common after the routine schedule, and after the meningococcal B vaccine in particular

Risk assessment: the traffic light system

NICE NG143 assesses five domains and takes the highest category scored in any one of them. A single red feature makes the child red, however green the rest of the assessment looks.¹

Tachycardia in the amber row is judged against age-specific thresholds, since a heart rate of 150 is normal in a neonate and alarming in a 5-year-old. Learn the respiratory rate cut-offs, which are the ones NICE names explicitly, and have a working sense of the normal ranges below.

Clinical features and examination

The history should establish the duration and pattern of the fever, feeding and fluid intake, urine output measured in wet nappies, activity and alertness compared with normal, and any focal symptoms. Ask about immunisation status against the current UK schedule, recent travel, contact with infectious illness, and whether the child is immunosuppressed or has an underlying condition such as sickle cell disease, congenital heart disease or an indwelling device.

Crucially, ask the parent whether this illness is different from previous ones. Parental concern that this is not like the usual is an independent predictor of serious illness and should never be discounted.

Examination essentials

• Full observations: temperature, heart rate, respiratory rate, oxygen saturation, capillary refill, and blood pressure in children over 12 months or where circulatory compromise is suspected
• General appearance: tone, alertness, whether the child engages with you or with a parent, and the quality of the cry
• Hydration: mucous membranes, skin turgor, sunken eyes, the fontanelle in infants, and the nappy count
• Whole-body skin inspection with the child undressed - looking specifically for a non-blanching rash, which requires you to look at all the skin including the nappy area and the soles
• Throat, ears and chest for a focus, plus abdominal palpation and inspection of every joint and limb for swelling or reluctance to move
• Neurological: neck stiffness, bulging fontanelle, and Kernig's and Brudzinski's signs - though these are unreliable in infants, where irritability and an abnormal cry may be the only clue

Investigations

What you order is determined by the risk category and the age of the child, not by the height of the temperature.¹

Infants under 3 months

All febrile infants under 3 months should be seen by a paediatric specialist and, unless there is a clear alternative explanation, receive a full septic screen:

• FBC, CRP and blood culture
• Urine for microscopy and culture - clean catch, or catheter or suprapubic aspirate if necessary
• Chest radiograph if there are respiratory signs
• Stool culture if there is diarrhoea
• Lumbar puncture in all infants under 1 month, in infants aged 1-3 months who appear unwell, and in infants aged 1-3 months with a white cell count below 5 or above 15 x10^9/L

Antibiotics should not be delayed while waiting to perform the lumbar puncture, and should be given first if the child is unstable or if there is any contraindication to the procedure.

Children of any age in the red category

• Blood culture, FBC, CRP, and a venous or capillary blood gas including lactate
• U&Es, LFTs and clotting if sepsis is suspected
• Blood glucose - hypoglycaemia is common, easily missed and immediately treatable
• Urine testing in every child
• Lumbar puncture unless contraindicated, with chest radiograph and stool culture as clinically indicated
• Meningococcal and pneumococcal PCR on blood, which remains positive for some days after antibiotics have been given

Amber category

Urine testing in all, plus blood tests and chest radiograph guided by the clinical picture, and consideration of lumbar puncture in children under 1 year. A period of observation in an ambulatory setting is often more informative than any single test - the trajectory over four hours tells you more than a CRP taken at hour one.

Green category

Urine testing for possible urinary tract infection, and no routine blood tests or imaging. These children are managed at home with clear safety netting.

Management

Disposition by risk category

Antimicrobial therapy

• Under 1 month: intravenous cefotaxime plus amoxicillin. The amoxicillin covers Listeria monocytogenes, which cephalosporins do not treat and which is a genuine pathogen in this age group.
• 1-3 months: intravenous cefotaxime or ceftriaxone, usually with amoxicillin added until listeriosis is excluded
• Over 3 months with suspected meningitis or meningococcal sepsis: intravenous ceftriaxone
• Community suspicion of meningococcal disease: intramuscular or intravenous benzylpenicillin before transfer, unless it would delay it
• Add vancomycin where recent foreign travel or prolonged or multiple antibiotic exposure raises the possibility of a resistant pneumococcus

Ceftriaxone is avoided in neonates under 1 month, particularly those who are jaundiced or receiving calcium-containing infusions, because it displaces bilirubin from albumin and can precipitate with calcium - which is exactly why cefotaxime is specified in that age group.⁷

Sepsis and shock

A febrile child with signs of shock is resuscitated on standard paediatric sepsis principles: high-flow oxygen, intravenous or intraosseous access, blood cultures, a broad-spectrum antibiotic within the first hour, and a fluid bolus of 10 mL/kg of a balanced crystalloid or 0.9% sodium chloride, reassessing after each bolus.² Take blood glucose and lactate at the same time. Escalate early to a senior clinician and to the retrieval team if more than 40-60 mL/kg is required, since that signals a need for inotropes and intensive care.

Antipyretics

Antipyretics treat discomfort, not temperature. NICE is explicit that paracetamol and ibuprofen should be considered in children who appear distressed, and should not be used with the sole aim of reducing the temperature.¹

Safety netting

This is the part of the consultation that most often carries the marks and, in practice, most often carries the risk. Parents of a child sent home should be given verbal and written advice covering:

• Offering fluids regularly, and continuing breastfeeding if breastfed
• Recognising dehydration: sunken fontanelle, dry mouth, sunken eyes, absent tears and fewer wet nappies
• How to check for a non-blanching rash with the tumbler test
• Checking on the child during the night
• Keeping the child away from nursery or school while febrile, and telling the setting
• Seeking urgent help if the child has a fit, develops a non-blanching rash, becomes less responsive, or if the parent simply becomes more worried
• A specific route back into care - who to call, and by when to seek review if the fever continues beyond 5 days

Fever without an apparent source

Around half of febrile children under 5 have no source identified at first assessment, and this group carries a disproportionate share of the risk. NICE recommends that a child with fever without apparent source who has any amber or red features be actively assessed for occult infection, with urine testing in all of them.

Where the fever has continued for 5 days or more without a source, widen the differential deliberately: Kawasaki disease, occult abscess, urinary tract infection, atypical pneumonia, tuberculosis, malignancy including leukaemia and neuroblastoma, systemic juvenile idiopathic arthritis, and imported infection such as malaria or enteric fever.

The temptation with a persistently febrile but reasonably well child is to keep repeating blood tests. A more productive strategy is careful repeat clinical examination, because new signs - a joint effusion, a murmur, hepatosplenomegaly, lymphadenopathy or a rash - frequently declare themselves over 48 hours and point directly at the diagnosis.

Complications

The complications are those of the underlying illness rather than of the fever itself. Delayed recognition of sepsis leads to shock, multi-organ failure and death; meningococcal disease can leave survivors with limb loss, deafness or neurological deficit; untreated urinary tract infection in an infant risks renal scarring and later hypertension.

Dehydration from reduced intake and increased insensible losses is common and is the usual reason an otherwise well child with a viral illness needs admission. Febrile convulsions occur in around 3% of children between 6 months and 6 years; they are frightening but benign, and are covered separately.

There are also iatrogenic harms worth naming: unnecessary antibiotics driving resistance and Clostridioides difficile infection, painful and unnecessary investigations, and the opposite harm of false reassurance drawn from a normal set of bloods taken too early in the illness.

Red flags

Prognosis

For the great majority of children the outlook is excellent: a viral illness that resolves within 3-5 days with fluids, comfort and time. Serious bacterial infection has become considerably less common in the UK since the introduction of Haemophilus influenzae type b, pneumococcal, meningococcal C and meningococcal B conjugate vaccines, which has genuinely changed the arithmetic of risk in the fully immunised child.⁵

That decline is precisely why unimmunised children matter so much. Falling MMR and routine schedule uptake has already produced measles outbreaks in the UK, and an incompletely immunised febrile child should be assessed against a different prior probability of invasive Haemophilus or pneumococcal disease. Always take and document the immunisation history.

Where the outcome is poor it is usually because of delay: an infant sent home without a urine sample, a purpuric spot never looked for because the child was not fully undressed, or reassurance drawn from a fever that settled after paracetamol.⁶ The structure of the NICE assessment exists to make those particular failures less likely, and using it visibly - documenting the category and the reason for it - is both good practice and what examiners are looking for.