Bronchiolitis and croup: the AU general-practice approach

Bronchiolitis and croup are the two most common acute viral airway syndromes presenting to Australian GPs and emergency departments through the cooler months. They look superficially similar — a distressed child with a cough and noisy breathing — but they are distinct conditions affecting different anatomical locations in different age groups, with entirely different management principles.

Bronchiolitis is an acute viral lower respiratory tract infection in infants under 12 months. RSV (respiratory syncytial virus) is the dominant pathogen; rhinovirus, human metapneumovirus, and parainfluenza virus also contribute. An estimated 10–30% of Australian infants experience bronchiolitis in any given year, and approximately 3% require hospital admission. RSV season typically runs April to August, peaking in winter.

Croup (laryngotracheobronchitis) is a viral upper-airway syndrome in children 6 months to 6 years, caused predominantly by parainfluenza virus. The characteristic barking cough results from subglottic oedema narrowing the paediatric airway. About 3% of children under 6 years are affected annually. Symptoms frequently worsen at night and can alarm parents, but most cases are mild and respond rapidly to a single dose of oral dexamethasone.

A significant development in Australian paediatric care is the 2024 introduction of RSV nirsevimab (Beyfortus) on the National Immunisation Program (NIP), alongside a funded maternal RSV vaccine in pregnancy. These immunisation strategies are expected to substantially reduce severe RSV bronchiolitis admissions in coming seasons — both represent important counselling points at antenatal and early postnatal visits.

A. Core clinical — the AU general-practice framework

Bronchiolitis: history and examination

Bronchiolitis follows a 2–4 day viral upper respiratory prodrome (coryza, low-grade fever), after which lower respiratory signs emerge: cough, tachypnoea, wheeze, and crackles with varying work of breathing. Feeding difficulty — because sucking and breathing compete — is a central severity indicator.

History to take:

• Age: the bronchiolitis definition is strict at under 12 months; beyond this age, recurrent wheeze suggests a different diagnosis
• Feeding intake as a percentage of normal; wet nappy count; vomiting
• Oxygen saturation if the family has a home pulse oximeter
• Gestational age at birth and any history of prematurity
• Known cardiac, lung, or neurological comorbidity
• Whether nirsevimab has been received, and whether the mother received Abrysvo in pregnancy
• Sick contacts; childcare attendance

Examination:

• Vital signs: respiratory rate, heart rate, SpO₂ (most important single measure)
• Work of breathing: subcostal and intercostal recession, suprasternal recession, nasal flaring, head bobbing, accessory muscle use
• Hydration: capillary refill time, anterior fontanelle, mucosal moisture, and urine output from history
• Auscultation: diffuse wheeze with crackles; reduced air entry in severe disease
• Mental state: alert and interactive versus lethargic or irritable

Severity assessment (clinical, no single validated score):

Severity	Features
Mild	Comfortable at rest; SpO₂ ≥95%; feeding ≥75% normal; mild chest recession
Moderate	SpO₂ 90–94%; feeding 50–75% normal; moderate recession; tachypnoea
Severe	SpO₂ <90%; feeding <50% normal; marked recession; apnoea; lethargy or cyanosis

Croup: history and examination

Croup presents after 12–48 hours of mild upper respiratory prodrome, then the barking cough — often appearing suddenly overnight. Inspiratory stridor develops as subglottic oedema progresses; stridor present at rest (not only with crying) signals moderate-to-severe disease.

The RCH Melbourne Croup CPG uses the Westley score to guide severity grading, assessing stridor, retractions, air entry, cyanosis, and consciousness level. The most clinically important question remains: is stridor present at rest?

Discriminators from upper-airway emergencies:

Condition	Key distinguishing features
Croup	6m–6y; barking cough; gradual onset; low-grade fever
Epiglottitis	Toxic child; drooling; tripod posture; hot potato voice; do not examine throat
Bacterial tracheitis	Toxic; copious secretions; no adrenaline response; IV antibiotics + airway management needed
Foreign body	Sudden onset choking; unilateral wheeze or asymmetric air entry
Anaphylaxis	Multi-system; allergen exposure; urticaria; stridor = airway component

If epiglottitis is suspected, call 000 immediately, keep the child calm and upright, and do not examine the airway — instrumentation can precipitate complete obstruction.

B. Bronchiolitis — what the evidence says

The PREDICT National Bronchiolitis CPG — endorsed across Australian paediatric emergency networks — provides a clear evidence summary: bronchiolitis management is supportive only. The evidence against common interventions is robust and consistent.

What does not work in bronchiolitis:

• Salbutamol: Multiple randomised trials and meta-analyses demonstrate no benefit. The pathophysiology matters: bronchiolitis involves viral epithelial damage and mucus plugging of small airways — not bronchospasm. The airways do not respond to beta-2 agonists as they do in asthma. eTG is explicit: bronchodilators are not indicated.
• Corticosteroids: Also ineffective in multiple trials. Dexamethasone helps croup because subglottic oedema is steroid-responsive; the small-airway pathology of bronchiolitis is not.
• Antibiotics: Bronchiolitis is viral; reserve antibiotics for confirmed bacterial superinfection, which is uncommon.
• Chest physiotherapy: Not supported by evidence.
• Nebulised hypertonic saline: Mixed evidence; not recommended as routine by PREDICT or RCH guidelines.
• Deep nasal suction: Gentle syringe-bulb suction before feeds is reasonable; vigorous deep suction is not recommended.

What supports recovery:

• Observation and monitoring — SpO₂, respiratory rate, feeding intake, and hydration at each review
• Oral hydration — breastfeeding or formula if tolerated; nasogastric or IV fluids if intake falls below 50% or hydration is compromised
• Oxygen — when SpO₂ falls below 90% (follow local hospital protocol; some centres now target ≥92%)
• High-flow nasal oxygen (HFNC) — for moderate-to-severe disease in hospital; reduces need for intubation in some settings

Admission criteria:

• Age under 3 months
• Born prematurely, or chronic lung disease, congenital cardiac disease, or neurological comorbidity
• Feeding below 50% of normal
• SpO₂ below 90–92% on room air
• Severe work of breathing or apnoea
• Social vulnerability making safe home monitoring impractical

Natural history: bronchiolitis peaks in severity day 3 to 5; the cough often persists for 2 to 3 weeks. Clear parental counselling on this course — with a written safety net — is the most important outcome of the GP encounter.

C. Croup — diagnosis and management

Unlike bronchiolitis, croup responds reliably to corticosteroids. Subglottic oedema is anti-inflammatory-responsive, and the treatment principle is straightforward: give dexamethasone early to any child with croup who presents for medical assessment, regardless of initial severity.

Dexamethasone

Per the RCH Croup CPG and eTG:

Severity	Dexamethasone dose
Mild (barking cough; no stridor at rest)	0.15 mg/kg oral, maximum 12 mg
Moderate (stridor at rest; mild retractions)	0.15–0.6 mg/kg oral
Severe (stridor at rest; marked retractions; agitation or drowsiness)	0.6 mg/kg oral or IM + transfer to ED

Prednisolone 1 mg/kg is an acceptable alternative when dexamethasone is unavailable, though dexamethasone’s longer duration of action (approximately 24 hours) makes it preferred. Onset occurs within 30–60 minutes.

Observation after dexamethasone: Observe for 2–4 hours. A child with mild-to-moderate croup who improves and has no stridor at rest can be safely discharged with clear safety-netting. AMH notes that parents should return if the barking cough worsens, stridor appears at rest, or the child seems unduly distressed.

Nebulised adrenaline for severe croup

When croup is severe — stridor at rest, marked retractions, agitation, drowsiness, or hypoxia — add nebulised adrenaline 1:1000 solution 5 mL (5 mg) via nebuliser. Onset is within 10 minutes. Effect lasts only 1–2 hours; observe for at least 2 hours after nebulised adrenaline before discharge, as symptoms can rebound. This is distinct from bronchiolitis management, where nebulised adrenaline has no role.

Managing the child and family

In croup, agitation worsens airway narrowing. Keeping both child and parent calm — through explanation, avoiding unnecessary examination, maintaining a quiet environment, and avoiding distressing procedures — is clinically important. Crying significantly increases the degree of stridor.

Recurrent croup

Children with two or more episodes of croup, or an atypical course, benefit from ENT or paediatric respiratory review to exclude laryngomalacia, subglottic stenosis, or haemangioma.

D. Australian operations

RSV prevention — what has changed

The Australian immunisation landscape for RSV changed significantly from 2024 onwards:

Nirsevimab (Beyfortus): A monoclonal antibody providing passive immunity against RSV. NIP-funded for infants ≤8 months at the start of their first RSV season, and for higher-risk infants up to 24 months (chronic lung disease of prematurity, haemodynamically significant congenital cardiac disease, severe immunodeficiency). Discuss timing with parents at antenatal and postnatal visits. Current eligibility criteria and scheduling are in the Australian Immunisation Handbook.

Maternal RSV vaccine (Abrysvo): NIP-funded for pregnant women at 28–36 weeks gestation. Maternal antibodies cross the placenta and protect the newborn from birth — particularly valuable for infants born before the RSV season window for nirsevimab dosing. See the Australian Immunisation Handbook for current scheduling.

Routine vaccination

The NIP schedule protects against other pathogens that cause or complicate these syndromes: DTPa (pertussis), pneumococcal (Prevenar), influenza (annual from 6 months). Review vaccination status at every acute paediatric encounter.

MBS billing

• Standard GP consultations: items 23 / 36 / 44 (level B/C/D)
• ATSI Health Assessment: item 715 for comprehensive review including growth and vaccination status
• Chest X-ray: item 58500 range — selective use; not indicated for typical bronchiolitis
• Telehealth: appropriate for parental advice and follow-up review of an improving child (existing relationship rule applies)

Parental counselling and safety-netting

• Bronchiolitis: peaks day 3–5; cough persists 2–3 weeks; no puffers or antibiotics needed; return for any admission criterion
• Croup: recurs night-time; the barking cough is loud but usually manageable; return for stridor at rest
• Avoid second-hand smoke — smoke exposure increases severity of both conditions
• Avoid OTC cough and cold preparations in children under 6 years: TGA advises against these due to lack of benefit and potential harm
• Childcare exclusion: until the child is well enough to attend

E. Special populations

Infants under 3 months. The admission threshold is low for this group — any feeding difficulty, increased work of breathing, or uncertain trajectory warrants hospital assessment. Apnoea is more common in very young infants with RSV.

Premature infants and those with chronic lung disease. RSV causes substantially more severe disease in infants with CLD of prematurity. Nirsevimab eligibility extends to 24 months for high-risk infants in this category. These children are more likely to require high-flow nasal oxygen or CPAP; involve paediatric services early.

Congenital heart disease. Children with haemodynamically significant CHD are at high risk of severe RSV bronchiolitis. Nirsevimab eligibility extends to 24 months for infants requiring cardiac medication or surgical management. Escalate early; involve the cardiologist in planning.

Aboriginal and Torres Strait Islander children. Risk of severe lower respiratory tract infection is higher, and social determinants may limit close home monitoring. Ensure NIP is current at every visit; use item 715 ATSI health assessment to review vaccination status and respiratory health; apply a lower admission threshold. HealthDirect has multilingual consumer resources.

Immunocompromised children. RSV and croup viruses can cause prolonged and severe disease in children on chemotherapy, post-transplant, or with primary immunodeficiency. Early specialist involvement and lower admission thresholds apply.

When to escalate

Call 000 or transfer to ED immediately:

• Suspected epiglottitis — drooling, tripod posture, hot potato voice, toxic appearance — do not examine the throat
• Suspected bacterial tracheitis — toxic child, copious secretions, no improvement with nebulised adrenaline
• Severe bronchiolitis — SpO₂ below 90%, apnoea, cyanosis, or extreme respiratory distress
• Severe croup — stridor at rest, marked retractions, agitation or drowsiness, or failure to respond to dexamethasone
• Suspected foreign body aspiration — sudden onset, choking episode, unilateral wheeze
• Anaphylaxis with airway involvement — administer IM adrenaline to the outer thigh immediately

Refer to paediatrics or paediatric respiratory physician:

• Recurrent croup (two or more episodes) — to exclude structural airway abnormality via ENT
• Recurrent wheeze beyond 12 months of age — assess for asthma
• Atypical bronchiolitis (child over 12 months, recurrent, unusually prolonged course)
• Persistent respiratory morbidity after severe bronchiolitis

What this article is and is not

This is general health information drawn from current Australian paediatric guidelines — the PREDICT National Bronchiolitis CPG, RCH Melbourne Clinical Practice Guidelines, the Australian Immunisation Handbook, Therapeutic Guidelines (eTG), and the Australian Medicines Handbook. It is not personal medical advice and does not replace assessment by your child’s GP or treating clinician.

If your child is in respiratory distress — blue lips, fast breathing, chest muscles visibly working with every breath, or unusual drowsiness — do not wait for a GP appointment. Call 000 or present directly to the nearest emergency department.

For Australian consumer resources: HealthDirect — Bronchiolitis, HealthDirect — Croup, Better Health Channel — Croup, RCH Kids Health Information.

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Sources cited

1. PREDICT National Bronchiolitis CPG
2. RCH Melbourne CPG — Bronchiolitis
3. RCH Melbourne CPG — Croup
4. Australian Immunisation Handbook
5. Therapeutic Guidelines (eTG)
6. Australian Medicines Handbook (AMH)
7. National Immunisation Program
8. TGA
9. HealthDirect — Bronchiolitis
10. HealthDirect — Croup
11. Better Health Channel — Croup
12. RCH Kids Health Information