Bronchiolitis in infants

Red Flags

Apnoea, severe respiratory distress (RR >70/min, intercostal and subcostal recession, head bobbing, grunting), or SpO2 <90% on room air — emergency admission and respiratory support^[1]
Poor feeding (<50% usual), dehydration signs, lethargy, or central cyanosis — admit; IV/NG fluids; high-flow oxygen^[1]
Age <3 months, ex-prematurity (<32 weeks), congenital heart or chronic lung disease, immunodeficiency — lower threshold for admission and observation^[1]
Worsening despite supportive care after 24 h or persistent SpO2 <92% on supplemental oxygen — escalate to high-flow nasal oxygen or CPAP; PICU consult^[1]

First-line treatment

Interventions

Supportive care as the foundation^[1]
Adequate oxygenation (target SpO2 ≥90–92%), nasal saline drops + bulb suction, small frequent feeds (NG if poor oral intake), upright positioning, watchful monitoring
Oxygen delivery and respiratory support^[1]
Low-flow nasal cannula for SpO2 <90%; high-flow nasal cannula (1–2 L/kg/min) for moderate-severe distress; CPAP or HFNC pre-PICU; intubation only if respiratory failure
Hydration and feeding support^[1]
NG feeds preferred over IV fluids when possible; isotonic IV fluids if NG not tolerated; avoid hypotonic fluids (SIADH risk)
Avoid ineffective therapies^[1]
Routine bronchodilators NOT recommended (no benefit); routine systemic or inhaled steroids NOT recommended; routine antibiotics NOT recommended; nebulised hypertonic saline only for inpatients with anticipated long stay
RSV prevention — passive immunisation^[1]
Nirsevimab single dose at start of RSV season for all infants entering first RSV season and at-risk infants in second season; palivizumab where nirsevimab unavailable, monthly during season for high-risk infants
Maternal RSVpreF vaccination^[1]
Maternal RSV vaccine at 32+0 to 36+6 weeks gestation provides passive antibody protection to newborn against RSV bronchiolitis

First-line drug therapy

Drug	Class	Adult	Paediatric	Notes
Nirsevimab^[1]	Long-acting anti-RSV F protein monoclonal antibody	Not applicable — paediatric prophylaxis	Infants <5 kg: 50 mg IM single dose; ≥5 kg: 100 mg IM single dose at start of RSV season; second-season at-risk: 200 mg IM	Replaces palivizumab in most settings; provides 5-month protection from one dose; reduces RSV bronchiolitis hospitalisation by ~80%
Palivizumab^[1]	Anti-RSV F protein monoclonal antibody	Not applicable — paediatric prophylaxis	15 mg/kg IM monthly throughout RSV season (max 5 doses)	Reserved for ex-prematurity, congenital heart disease, chronic lung disease where nirsevimab not available; replaced by nirsevimab in most national programmes from 2024
Nebulised hypertonic 3% saline (selected inpatients)^[1]	Mucolytic / hyperosmolar	Not applicable — paediatric prophylaxis	4 mL nebulised every 2–4 h for first 24 h then less frequent	Inpatients with anticipated stay >24 h; not for outpatient use; pre-treat with bronchodilator if reactive airways concern

Nirsevimab^[1]

Long-acting anti-RSV F protein monoclonal antibody

Adult: Not applicable — paediatric prophylaxis
Paediatric: Infants <5 kg: 50 mg IM single dose; ≥5 kg: 100 mg IM single dose at start of RSV season; second-season at-risk: 200 mg IM

Replaces palivizumab in most settings; provides 5-month protection from one dose; reduces RSV bronchiolitis hospitalisation by ~80%

Palivizumab^[1]

Anti-RSV F protein monoclonal antibody

Adult: Not applicable — paediatric prophylaxis
Paediatric: 15 mg/kg IM monthly throughout RSV season (max 5 doses)

Reserved for ex-prematurity, congenital heart disease, chronic lung disease where nirsevimab not available; replaced by nirsevimab in most national programmes from 2024

Nebulised hypertonic 3% saline (selected inpatients)^[1]

Mucolytic / hyperosmolar

Adult: Not applicable — paediatric prophylaxis
Paediatric: 4 mL nebulised every 2–4 h for first 24 h then less frequent

Inpatients with anticipated stay >24 h; not for outpatient use; pre-treat with bronchodilator if reactive airways concern

Safety-net

Symptoms typically peak at days 3–5 and resolve over 1–2 weeks; cough may persist 3–4 weeks^[1]
Return same-day if breathing becomes faster or harder, baby cannot feed, becomes drowsy/floppy, lips look blue, or fewer than half normal wet nappies^[1]
Hand hygiene and avoiding tobacco smoke exposure reduce respiratory infections; older siblings often bring viruses home^[1]

Referral criteria

Apnoea, severe distress, hypoxia, dehydration, or age <3 months with moderate-severe diseaseEmergency department / paediatric admission^[1]
Worsening despite high-flow nasal cannula or CPAPPaediatric intensive care^[1]
High-risk infants entering RSV season without prophylaxisCommunity paediatrics / immunisation clinic for nirsevimab or palivizumab^[1]
Recurrent or atypical bronchiolitis at age >18 months or >2 episodesPaediatric respiratory medicine — consider asthma, immunodeficiency, anatomical airway lesion^[1]

Clinical summary

Diagnosis and supportive care for acute viral bronchiolitis in infants <2 years; nirsevimab and palivizumab prophylaxis pathways.

References

1.AAP Clinical Practice Guideline: Diagnosis, Management, and Prevention of Bronchiolitis (2014, with 2023–2024 nirsevimab updates); WHO Pocket Book of Hospital Care for Children (2024)