Pediatrics & Emergency Medicine & Family Medicine
Fièvre de l'enfant | Clinique Omicron Québec
Fever is defined as a rectal body temperature of 38.0°C or higher in children—it is the most common reason for pediatric visits, accounting for 20 to 30% of visits to emergency departments and clinics. In the vast majority of cases, it is viral in origin, benign, and self-limiting, but it can be the first sign of a severe bacterial infection (meningitis, bacteremia, upper urinary tract infection, bacterial pneumonia) or an inflammatory disease. Fever is a physiological adaptive response: the rise in temperature inhibits the replication of many pathogens, stimulates the immune response (T-cell proliferation, interferon production), and accelerates phagocytosis. It is therefore not inherently dangerous in the vast majority of cases and does not require systematic treatment for this reason alone—the goal of antipyretic treatment is the child’s comfort, not normalizing the temperature reading. The evaluation of a febrile child is based on a stratified approach according to age (infants under 3 months are at high risk of serious bacterial infection even without localized symptoms), the general clinical presentation (is the child well-appearing or does he or she show signs of severe illness?), and the presence or absence of an identifiable source of infection. In Quebec, the pediatric guidelines of the Canadian Paediatric Society (CPS) and CHU Sainte-Justine serve as the reference standards for the management of fever in children.
Definitions, temperature measurement, and initial clinical evaluation
- Definitions and temperature thresholds according to the measurement method: fever: rectal temperature ≥38.0°C — rectal measurement is the gold standard in infants and children under 2 years old; severe hyperthermia: rectal temperature ≥40.0°C — associated with a higher probability of bacterial infection but not specific (many viral infections cause temperatures >40°C); measurement methods and approximate equivalences: rectal (gold standard): ≥38.0°C = fever — axillary: ≥37.4°C (less reliable — often underestimates actual temperature by 0.5–1.0°C — not recommended in infants) <2 ans) — tympanique infrarouge : ≥38,0 °c (fiabilité variable selon la technique + l'âge le conduit auditif externe du nourrisson est court et courbe → lectures variables) frontale (temporale) (variabilité les modèles transpiration moins fiable que rectale chez nourrisson) buccale ≥37,8 (possible dès 4–5 ; recommandations de scp sur méthode mesure <2 ans ou (tympanique 3 mois) 2–5 axillaire>5 years old → oral or tympanic + forehead measurement is acceptable for screening but not for deciding on hospitalization in infants; general clinical assessment — the «Pediatric Assessment Triangle» (PAT): appearance (A): tone + interaction + gaze + consolability + crying — circulation (C): skin color (pallor + mottling + cyanosis) + capillary refill — respiratory effort (R): respiratory rate + signs of distress (intercostal retractions + nasal flaring + grunting) — a child with an abnormal PAT → immediate urgent management regardless of temperature
- Risk Stratification by Age - Quebec Pediatric Approach: Newborns aged 0 to 28 days (febrile newborn): any newborn with a temperature ≥38.0 °C → systematic hospitalization + complete sepsis workup (blood culture + urine culture + lumbar puncture + CBC + CRP + PCT — procalcitonin) + immediate empirical IV antibiotic therapy without waiting for results → high risk of severe bacterial infection (SBI) including Group B Streptococcus + Listeria + E. coli + Herpes simplex (neonatal herpes encephalitis → systematic IV acyclovir if clinical suspicion); infant aged 29 days to 3 months: any infant between 1 and 3 months with T° ≥38.0 °C → urgent medical evaluation — stratification by biological criteria: low-risk criteria (NICE + Rochester + Philadelphia + Step-by-step — Mintegi): well-appearing + absence of identified bacterial focus + CBC: white blood cells 5–15 G/L + bands (immature) 1.5 G/L + PCT <0.5 ng/mL + CRP <20 mg/L + negative urine culture → outpatient monitoring possible with check-up at 24–48h — high-risk criteria or toxic appearance: hospitalization + workup + IV antibiotics + lumbar puncture according to the Sainte-Justine University Hospital Centre algorithm; child aged 3 months to 36 months (3 years): fever without source (FWS) — no infectious source identified on examination → lower risk of BSI than before 3 months but not negligible — assessment according to general appearance + fever height + vaccination status (vaccinated vs unvaccinated child against Hib + pneumococcus) + duration; child over 3 years: low risk of BSI in a well-appearing vaccinated child — clinical focus usually identifiable (ENT + respiratory + urinary) — management according to identified focus
- Common causes of fever in children by age: viral causes (70–80% of childhood fevers): nasopharyngitis (respiratory viruses: rhinovirus, coronavirus, RSV, and metapneumovirus) + viral pharyngitis + laryngitis + bronchiolitis (RSV — infants) <24 mois) + grippe (influenza a et b) otite virale gastro-entérite (norovirus rotavirus) exanthèmes viraux (roséole exanthème subit ="HHV-6" — fièvre élevée3–5 jours puis rush → très fréquente entre 6 mois 2 ans rubéole varicelle coxsackie maladie mains-pieds-bouche) covid-19 adénovirus ; causes bactériennes (10–15 %) : moyenne aiguë bactérienne (la cause la plus chez l'enfant s. pneumoniae h. influenzae m. catarrhalis) pharyngite à streptocoque du groupe (streptocoque bêta-hémolytique sbga test rapide de détection antigénique >5 days + criteria + risk of coronary aneurysms → urgent IVIG) + systemic juvenile idiopathic arthritis (sJIA) + PFAPA (periodic fever, aphthous stomatitis, pharyngitis, adenitis) + pediatric lupus
Child fever management
| Clinical situation | Evaluation, causes, and diagnostic approach | Treatment and practical recommendations |
|---|---|---|
| Antipyretic treatment — acetaminophen and ibuprofen Child Comfort — Dosage by Weight |
The goal of antipyretic treatment is to improve the child’s comfort, not to bring the temperature back to normal at all costs—a fever that is well tolerated by a child who appears healthy does not necessarily require antipyretic treatment; acetaminophen (Tylenol + generics): first-line medication—indications: all ages, including infants <3 months if prescribed by a physician — dosage: 15 mg/kg/dose PO (or rectal) — minimum interval between doses: 4–6 hours — maximum daily dose: 75 mg/kg/day (absolute maximum 4,000 mg/day in children >12 years) — available as an oral suspension (80 mg/mL or 160 mg/5 mL — check the concentration on the bottle — a common source of dosing errors) + suppositories (80 mg + 120 mg + 325 mg) + tablets (325 mg + 500 mg — once the child is able to swallow); ibuprofen (Advil + Motrin + generics): second-line medication or alternative — indications: children over 6 months (contraindicated in infants <6 months — renal risk + insufficient data) — dosage: 5–10 mg/kg/dose PO — minimum interval: 6–8 hours — maximum dose: 40 mg/kg/day (maximum 2,400 mg/day) — advantage: longer duration of action (6–8 hours vs. 4–6 hours for acetaminophen) — contraindications and precautions: severe dehydration + gastroenteritis with repeated vomiting (risk of nephrotoxicity if hypovolemia) + unstable asthma (prostaglandin inhibitors — may trigger bronchospasm in some asthmatics — use with caution) + chickenpox (risk of streptococcal necrotizing fasciitis → avoid NSAIDs in chickenpox) + any suspicion of severe bacterial infection (masks signs of worsening); alternating acetaminophen and ibuprofen: common practice but controversial—some studies show better antipyretic efficacy with alternating use vs. monotherapy—increased risk of dosing errors + complexity for parents—the SCP does not recommend systematic alternating use but does not contraindicate it if the child is very uncomfortable and the correct doses are followed; aspirin: strictly contraindicated in children and adolescents under 18 years of age with a viral infection → risk of Reye’s syndrome (encephalopathy + liver failure — rare but serious) | Physical measures and general recommendations for parents: Hydration: Increase fluid intake (water + broth + diluted juice) — fever increases insensible losses — goal: clear and frequent urination — breastfeeding on demand if infant is breastfed; Clothing: Undress the child — a child dressed too warmly can worsen their fever — light clothing + light blanket — do not cover to «sweat it out»; Lukewarm baths: Bath at 36–37°C (lukewarm water — NOT cold water which causes shivering + paradoxical vasoconstriction) — limited effectiveness over time but can temporarily improve comfort — no rubbing with alcohol (toxicity via skin absorption) + never use alcohol baths to treat fever; Room temperature: Room at 18–20°C; When to give antipyretics: If the child is uncomfortable + irritable + in pain — not routinely for fever 48–72h in a well child over 3 months old + fever that reappears after 24h of being fever-free (biphasic — certain viral infections + occult bacteremia) + any warning sign (see emergency section) |
| Fever in an infant under 3 months Emergency - Systematic Assessment |
Infants younger than 3 months are at the highest risk for serious bacterial infection (SBI) when they have a fever—their immune response is immature, and the clinical presentation is often misleading (an infant with meningitis may appear relatively well); epidemiology of SBI risk in febrile infants: 0–28 days: SBI risk 15–20% (meningitis + bacteremia + urinary tract infection + omphalitis + osteomyelitis) + neonatal herpes (high mortality risk) → hospitalization + comprehensive evaluation + systematic IV antibiotics; 29–60 days: BSI risk 5–10 % — risk stratification criteria (Mintegi step-by-step algorithm + NICE 2019 criteria): low risk (all criteria met): appears well + white blood cells 5–15 G/L + band cells <1.5 G/L + procalcitonin (PCT) <0.5 ng/mL + CRP <20 mg/L + negative rapid urine culture → outpatient monitoring with follow-up in 24 hours → 98–99% sensitivity % for detecting a urinary tract infection; high risk (a single abnormal criterion) or toxic presentation → hospitalization + comprehensive workup + IV antibiotic therapy + PL according to local protocol; 61–90 days: risk of BSI 2–5 % — similar stratification but slightly adjusted laboratory thresholds — PCT remains the best single biomarker for identifying a BSI (superior to CRP at 6–12 hours); diagnostic workup for febrile infants <3 months: CBC + differential count + CRP + PCT (if available) + blood culture (2 bottles) + urine culture via catheterization (standard) or suprapubic puncture — NOT via collection bag (frequent contamination) + chest X-ray if respiratory distress or tachypnea + lumbar puncture (LP): routine in infants <28 days + indicated according to the algorithm and appearance in infants 29–90 days + CSF analysis: appearance + cell count + proteinuria + glycosuria + bacteriology + Herpes simplex virus (HSV) PCR; empirical antibiotic therapy for febrile infants <3 months: IV ampicillin (50 mg/kg/dose — 3–4 doses/day) + IV gentamicin (or third-generation cephalosporin according to protocol) → covers SBGA + Listeria + Gram-negative bacteria + if neurological signs or seizures → IV aciclovir (20 mg/kg/dose × 3/day) immediately while awaiting CSF PCR results for HSV | Parental education and key messages for parents of a febrile infant: any infant under 3 months old with a temperature ≥38.0 °C → same-day medical consultation — do not wait and do not attempt home treatment without medical advice — do not give ibuprofen before 6 months old; warning signs to absolutely know: inconsolable crying or conversely weak whimpering + hypotonia (limp + floppy) + feeding difficulties (refusal of breast or bottle) + gray or mottled complexion + bulging fontanelle (sign of intracranial tension) + stiff neck + rash or red/purple spots + rapid breathing + cyanosis → immediate pediatric emergency (call 911 or nearest emergency room); for parents: fever itself does not «burn the brain» — only extreme temperatures (>42 °C — non-febrile malignant hyperthermia) can be dangerous — the main concern is not the height of the fever but the child's general appearance; home management: rectal thermometer is mandatory for infants — take temperature when the child is calm + note the time + the temperature + any medications given + answer the doctor's questions during the consultation; access to care in Quebec: pediatric urgent care clinic (GPU — guichet d'accès pédiatrique) + CHU Sainte-Justine emergency room + CHU de Québec emergency room + 811 Info-Santé (nurses) for guidance + Omicron Clinic telemedicine for rapid initial assessment in a well-appearing child over 3 months old |
| Febrile urinary tract infection (pyelonephritis) 2nd cause of UTI in children - Mandatory urine culture |
Febrile urinary tract infection (FUTI)—acute pyelonephritis—is the second leading cause of serious bacterial infection in children after meningitis, and the leading cause of bacterial infections in infants between 3 and 24 months of age following routine vaccination against Hib and pneumococcus; epidemiology: 5–10 per 100,000 febrile girls under 5 years of age + 1–2 per 100,000 boys after the first year of life (common in uncircumcised boys <12 months — a non-retractable foreskin promotes colonization by E. coli) — Initial presentation is often atypical in infants (isolated fever without urinary symptoms + irritability + feeding difficulties); causative organisms: E. coli (80–85% of cases) + Klebsiella pneumoniae + Proteus mirabilis + Enterococcus faecalis + Pseudomonas (children with urological abnormalities); risk factors: female gender after 12 months + uncircumcised boys <12 months + urological abnormalities (vesicoureteral reflux — VUR + obstructive uropathy) + history of UTIs + chronic constipation + bladder dysfunction; diagnosis: urine culture via catheterization (gold standard) or suprapubic aspiration in infants (<2 years) — urine dipstick (UD): leukocyturia + nitrites — sensitivity of UD in detecting UTI: 92–95% (%) — A negative BU in a healthy child has a high NPV → may avoid routine catheterization in recent guidelines (NICE 2022) — mandatory urine culture — diagnostic criteria: leukocyturia >10 leukocytes/mm³ (or >5 per high-power field) + significant bacteriuria (>10⁵ CFU/mL in a clean-catch urine sample or >10⁴ via catheterization) + monomicrobial culture; additional tests: CBC + CRP + PCT (elevated in pyelonephritis) + blood culture if infant <3 months or toxic presentation (E. coli bacteremia accounts for 5–10% of infant pyelonephritis cases) + renal ultrasound within 72 hours if first febrile urinary tract infection + lack of response to antibiotics at 48 hours | Treatment of febrile urinary tract infection in children: first-line oral antibiotic therapy if the child is >3 months old, appears well, and is able to eat: cefixime (Suprax): 8 mg/kg/day PO in a single dose × 7–14 days (first-line treatment — spectrum covering E. coli — low resistance rates in Quebec) + cephalexin (Keflex): 25–50 mg/kg/day in 4 doses × 10 days (less convenient than cefixime) + amoxicillin-clavulanic acid (Clavulin): 40 mg/kg/day of amoxicillin in 3 doses — adjust based on antibiogram upon receipt + TMP-SMX (Septra): increasingly less used as first-line therapy (growing resistance >20% % in North America); IV antibiotic therapy if: infant <3 months + toxic appearance + vomiting + inability to feed + known severe urological abnormality: IV cefotaxime (150 mg/kg/day in 3–4 doses) or IV ceftriaxone (50–75 mg/kg/day in 1 dose) × 2–4 days, then switch to oral therapy based on the antibiotic susceptibility test; total duration of treatment: febrile UTI (pyelonephritis): 10–14 days — uncomplicated cystitis (fever <38 °C + no signs of upper tract involvement): 3–5 days; post-UTI urological evaluation: SCP 2021 — 1st febrile UTI with good response: renal and bladder ultrasound (mandatory) + retrograde cystography (voiding cystourethrography — VCUG): only if ultrasound abnormality + recurrent UTI + boy <2 years with UTI + poor response to treatment — no longer routinely recommended after any first UTI since the 2021 revision of SCP guidelines (reduction of unnecessary invasive investigations); antibiotic prophylaxis (TMP-SMX 2 mg/kg/night × 12 months): if documented grade III–V vesicoureteral reflux + recurrent UTI (>2 febrile UTIs in 6 months) |
| Febrile seizure Simple vs. Complex — What to do |
Febrile seizures are the most common and most alarming complication of fever in children—they occur in 2–5% of children between 6 months and 5 years of age (with peak incidence at 14–18 months) and are generally benign; pathophysiology: fever lowers the seizure threshold in genetically predisposed children—voltage-gated sodium channels in neurons are temperature-sensitive—strong familial predisposition (if 1 parent has a history of febrile seizures → 25% risk; 2 parents → 50% risk); definition and classification: simple febrile seizure (85–90% of cases): cumulative criteria → T° ≥38.0 °C + generalized tonic-clonic seizure + duration <15 min + a single episode within 24 hours + spontaneous resolution without prolonged postictal deficit + child aged 6 months to 5 years + no prior neurological history + no CNS infection — excellent prognosis — risk of febrile seizure recurrence: 30–40 febrile seizures (including 15 febrile seizures during the same febrile episode) — slightly increased risk of subsequent epilepsy compared to the general population but by no means inevitable: 2–3 febrile seizures vs. 1 febrile seizure in the general population; complex febrile seizure (10–15% of cases): at least one of the following criteria → duration >15 min (febrile status epilepticus) + focal (partial) + recurrence within 24 hours + prolonged postictal neurological deficit (>1 hour — Todd’s paralysis) + child <6 months or >5 years → mandatory investigation + higher risk of subsequent epilepsy; differential diagnosis of febrile seizure: meningitis/encephalitis (CSF mandatory if neck stiffness + photophobia + purpura + meningeal signs + <12–18 months where meningeal signs are less reliable + complex febrile seizure) + hypoglycemia (blood glucose upon admission) + hyponatremia (complete blood count + electrolyte panel) + herpes encephalitis (IV acyclovir if encephalitic signs) | Management of ongoing febrile seizure (status epilepticus): recovery position (recovery position) + time the seizure + nothing in the mouth + do not restrain the child — if seizure >5 min → emergency anticonvulsant treatment: rectal diazepam (Diastat): 0.5 mg/kg PR (maximum 20 mg) — available in pre-filled syringe — to have at home if child with history of complex febrile seizure or status epilepticus + oral or nasal midazolam (Versed): 0.2 mg/kg (maximum 10 mg) — intranasal or oral route — as effective as rectal diazepam — easier for parents to administer + IV lorazepam (Ativan): 0.1 mg/kg IV if IV access available (emergencies); if seizure does not resolve after 2 doses of benzodiazepines (febrile status epilepticus) → IV phenobarbital + consult neurology + admission to intensive care; simple febrile seizure post-ictal workup: NO routine biological or brain imaging workup in simple febrile seizure in a well-appearing child aged 6 months to 5 years after the seizure — CBC + blood glucose if clinically indicated (suspicion of hyponatremia or hypoglycemia) — LP: indicated if <12–18 months + meningeal signs + complex febrile seizure + toxic post-ictal appearance — EEG: not indicated after a 1st simple febrile seizure — indicated if complex febrile seizure + frequent recurrences + diagnostic uncertainty; prophylaxis of recurrence: routine antipyretic treatment during a subsequent febrile episode does NOT prevent recurrence of febrile seizures (febrile seizures often occur during the initial rise in fever, before parents notice the fever) — parent education and de-escalation are essential — rectal diazepam or nasal midazolam at home if history of complex febrile seizure or if significant justified parental anxiety + long-term prophylactic antiepileptic treatment (valproate): reserved for recurrent complex febrile seizures + specialized neurological decision — benefits generally do not outweigh risks in simple febrile seizures |
| Kawasaki disease and prolonged fever in children Fever > 5 days — causes not to miss |
A fever lasting more than 5 days in a child requires a systematic diagnostic approach and the active exclusion of Kawasaki disease—an inflammatory vascular disease that can lead to permanent coronary aneurysms if left untreated; Kawasaki disease (KD): vasculitis of medium-sized vessels—the leading cause of acquired heart disease in children in developed countries—incidence in Quebec: 15–25 cases/100,000 children <5 years of age + peak incidence between 6 months and 5 years of age + male predominance (M/F 1.5:1) + winter and spring flare-ups; classic diagnostic criteria for Kawasaki disease: fever lasting ≥5 days + at least 4 of the following 5 criteria: bilateral non-purulent conjunctivitis (without purulent discharge) + changes in the lips and oral cavity (red/cracked lips + strawberry tongue + redness of the mucous membranes) + polymorphic rash (morbilliform erythema + scarlet-like erythema — often begins in the inguinal folds in infants) + erythema and edema of the hands and feet (acute phase) + desquamation of the extremities (subacute phase, days 10–25—characteristic periungual desquamation) + cervical lymphadenopathy ≥1.5 cm (often unilateral); Incomplete (subclinical) Kawasaki disease: fever ≥5 days + 2–3 clinical criteria + confirmation by echocardiography (coronary artery dilation) or laboratory criteria (CRP + ESR + albumin + white blood cell count + anemia + thrombocytosis) → 2017 AHA algorithm for incomplete Kawasaki disease; Laboratory workup in Kawasaki disease: CBC (leukocytosis + thrombocytosis in the subacute phase) + very high ESR + very high CRP + low albumin + AST + ALT + bilirubin + urinalysis (sterile pyuria) + ferritin — echocardiography (required at diagnosis + at 2 weeks + at 6–8 weeks); other causes of prolonged fever (>5–7 days) in children: bacterial infections (endocarditis + osteomyelitis + septic arthritis + deep abscess — abdominal-pelvic CT scan + bone scan) + prolonged viral infections (EBV + CMV + adenovirus) + systemic juvenile idiopathic arthritis (pediatric Still’s disease — transient salmon rash + arthritis + very high ferritin) + acute leukemia (complete blood count + smear + bone marrow aspiration) + lymphoma | Treatment of Kawasaki disease: urgent treatment—must be initiated within the first 10 days of fever to prevent coronary aneurysms; intravenous immunoglobulin (IVIG): 2 g/kg IV as a single 10–12-hour infusion — standard of care — reduces the risk of coronary aneurysms from 25% to <5% — optimal efficacy if administered before day 10 of fever — adverse effects: transfusion reactions (fever + chills + hypotension) → close monitoring during infusion; aspirin: 80–100 mg/kg/day PO in 4 divided doses (anti-inflammatory dose) during the febrile phase → reduction to antiplatelet dose (3–5 mg/kg/day in 1 dose) after 48 hours of afebrile status → continue for 6–8 weeks or until coronary arteries normalize — exception to the general rule of not giving aspirin to children: in MK, aspirin is the standard of care + the risk of Reye’s syndrome in this context is negligible; resistance to IVIG (persistent fever or recurrence >36 hours after the end of the infusion): second dose of IVIG + corticosteroids (IV methylprednisolone 30 mg/kg/day × 1–3 days) + IV infliximab (5 mg/kg — anti-TNF) in refractory cases; cardiological monitoring: echocardiography at diagnosis + on Day 14 + on Day 21 + at 6–8 weeks + documented coronary aneurysm → lifelong cardiological follow-up + anticoagulation based on aneurysm size (aspirin ± warfarin ± heparin according to the Z-score); pediatric multisystem inflammatory syndrome associated with COVID-19 (MIS-C — PIMS): presentation similar to Kawasaki disease + signs of shock + myocarditis + hyperferritinemia + very high CRP + positive SARS-CoV-2 serology → IVIG + aspirin ± methylprednisolone + consultation with cardiology + pediatric intensive care depending on severity |
ℹ️
Fever is not the enemy — fever phobias and advice for parents: «Fever phobia» is a well-documented phenomenon: many parents fear that fever itself causes brain damage, seizure, or death. These fears are largely unfounded. Fever is a useful defense mechanism and does not cause brain damage at temperatures encountered during common infections (even at 104–106 °F). What matters is the child's overall appearance, not just the number on the thermometer. A child who is playing, drinking, and responding normally at 103.1 °F is less concerning than a child who is apathetic, difficult to wake, or refusing to eat at 100.8 °F.
Warning Signs — Immediate Pediatric Emergencies (911 or ER)
Infant < 3 months with T° ≥38.0 °C → Urgent medical consultation on the same day — do not treat at home and wait.
Purpura (red/purple spots that do not blanch when pressed) + fever → meningococcemia → 911 → emergency department → IV penicillin G without delay.
Stiff neck + photophobia + severe headaches + projectile vomiting → Bacterial meningitis → immediate pediatric emergency.
Fever ≥5 days in children under 5 years old Kawasaki disease to exclude → mandatory medical consultation + echocardiogram.
Feverish infant with hypotonia, weak grunts, feeding refusal, bulging fontanelle, or gray/mottled skin sepsis or severe infection → immediate pediatric emergency.
Consult at Clinique Omicron
Clinique Omicron's physicians and nurse practitioners assess well-appearing febrile children over 3 months of age via in-person or telemedicine consultations, prescribe initial investigations if indicated (urinalysis + CBC + CRP), and refer to pediatric emergency services if alarm criteria are met. For infants under 3 months, a consultation at a university hospital's pediatric emergency department is recommended as a priority. Pediatric consultations are available at several service points in Quebec. To book an appointment, visit cliniqueomicron.ca.
The content of this page is for informational purposes only and does not replace the evaluation of a doctor or nurse practitioner. If you have any concerns about a child's fever, consult a healthcare professional without delay.
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