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Health condition · Clinically reviewed

Bronchiolitis, RSV, what to watch for and how the UK now prevents it.

A common winter illness in babies under two. Most manage at home, some need hospital, and prevention has changed for good with nirsevimab and maternal RSV vaccination.

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Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against NICE NG9, RCPCH and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK practice including nirsevimab roll-out and maternal RSV vaccination programmes.

Key facts

Bronchiolitis at a glance.

The essentials, in plain English. What it is, who gets it, how it usually plays out and what has changed in prevention.

  • What it is

    A lower respiratory tract viral infection with inflammation of the tiny bronchioles in infants under two years, peaking at three to six months.

  • Main cause

    Respiratory syncytial virus (RSV) accounts for around seventy per cent of cases. Other viruses include metapneumovirus, parainfluenza, adenovirus, influenza, rhinovirus and COVID.

  • Seasonality

    A UK winter illness, running from November through March, when RSV circulation peaks each year.

  • High-risk infants

    Premature babies, infants under twelve weeks, and those with chronic lung disease, congenital heart disease, Down syndrome, immunocompromise or neuromuscular conditions.

  • Typical course

    Two to three days of coryza and fever, then five to seven days of cough, wheeze and feeding difficulty before slow recovery over two to three weeks.

  • What has changed

    Nirsevimab, a single-dose long-acting antibody, and maternal RSV vaccination (Abrysvo) are transforming prevention across the UK.

Why this guide matters

Watch closely, treat gently, prevent early.

Bronchiolitis is common, usually self-limiting and rarely helped by medicines. The three points below shape the whole page.

  • Most care is supportive

    Nasal saline, small frequent feeds, oxygen if needed and time. That is what changes outcomes, not inhalers or steroids.

  • Knowing when to escalate saves lives

    Apnoea, low oxygen, poor feeding and severe respiratory distress are the red flags parents and clinicians need to recognise early.

  • Prevention has changed

    Nirsevimab for infants and Abrysvo for pregnant women are cutting severe RSV disease across the UK from 2024 onwards.

How the diagnosis is made

From runny nose to a clear plan.

The steps a UK GP, paediatrician or hospital team will normally follow, in order. So you know what to expect and why.

  1. 01

    Assessing

    Clinical assessment

    Bronchiolitis is a clinical diagnosis. A history of coryza followed by cough, wheeze, tachypnoea and feeding difficulty in an infant under two is enough.

  2. 02

    Assessing

    Severity check

    Oxygen saturation, work of breathing, feeding, hydration and apnoea history decide whether care can be at home or needs admission.

  3. 03

    Assessing

    Risk stratification

    Age under twelve weeks, prematurity, chronic lung disease, congenital heart disease or immunocompromise all lower the threshold for admission.

  4. 04

    Confirming

    Viral PCR from a nasal swab

    A nasopharyngeal aspirate can identify RSV and other viruses. It is not needed for every infant but helps in hospital for cohorting.

  5. 05

    Confirming

    Chest X-ray only when needed

    Not routine. Reserved for severe, atypical or complicated presentations where consolidation or another cause is suspected.

  6. 06

    Preparing

    Bloods and cultures if unwell

    FBC, CRP, blood culture and blood gas are selective, used when bacterial co-infection is suspected or the infant is severely unwell.

  7. 07

    Preparing

    Safeguarding and social review

    Household smoking, housing, parental confidence and safeguarding concerns are part of every assessment, alongside a urine culture in febrile infants under three months.

Typical timeline: assessment to a settled plan in a single visit for most families.

Symptoms

What bronchiolitis actually looks like.

The classic pattern: a couple of days of cold, then a spell of cough, wheeze and feeding difficulty. And the features that mean it is time to escalate.

  • Coryza and cough

    Runny nose, sneezing and a mild fever for two to three days, then a worsening cough that becomes the dominant symptom.

  • Wheeze and crackles

    Widespread high-pitched wheeze with fine bilateral inspiratory crackles on listening, and a hyperinflated chest.

  • Fast breathing

    Tachypnoea with a respiratory rate above fifty to sixty breaths per minute, often the earliest sign of trouble.

  • Increased work of breathing

    Nasal flaring, tracheal tug, subcostal recession, use of accessory muscles and grunting on expiration.

  • Feeding difficulty

    Taking less than half of usual feeds, tiring quickly at the breast or bottle, and passing fewer wet nappies.

  • Apnoea in young infants

    Pauses in breathing, particularly in babies under six weeks or those born prematurely. A clear reason for admission.

  • Low oxygen levels

    A saturation below ninety-two per cent in air is a threshold for hospital admission and oxygen therapy.

  • Red flag - exhaustion or cyanosis

    Grunting, silent chest, blue lips or a floppy exhausted baby needs a 999 response.

Treatment

How bronchiolitis is treated in the UK.

Supportive care at home for most infants, oxygen and feeding support in hospital for some, and PICU care for the sickest. Under NICE NG9, medicines have a very small role.

  • Supportive care first

    Nasal saline drops and gentle suctioning, upright positioning, minimal handling and small frequent feeds are the foundation of care at home and in hospital.

  • Humidified oxygen

    Given when saturations drop below ninety-two per cent in air, delivered by nasal cannula or head box in hospital.

  • Nasogastric or IV fluids

    Used when the infant cannot feed safely, is dehydrated or has had apnoea. NG feeding is preferred where possible.

  • High-flow nasal oxygen (HFNO)

    For moderate to severe disease on the ward. Reduces work of breathing and often prevents the need for intubation.

  • CPAP and PICU care

    CPAP, intubation and mechanical ventilation are reserved for respiratory failure or recurrent apnoea, delivered on a paediatric intensive care unit.

  • Medicines that are not recommended

    NICE NG9 does not recommend bronchodilators, nebulised adrenaline, hypertonic saline, steroids, antibiotics, montelukast or ribavirin routinely. They do not change outcomes.

  • Palivizumab (Synagis)

    A monthly monoclonal antibody given October to March, reserved for a small group of very high-risk infants under long-standing NICE criteria.

  • Nirsevimab (Beyfortus)

    A single-dose long-acting antibody, JCVI-recommended for universal infant use under twelve months and rolling out across the UK from 2024. A prevention game-changer.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your GP, midwife, health visitor or paediatric team knows your baby and can tell you which parts apply. If in doubt, get seen.

  • NICE. Bronchiolitis in children: diagnosis and management (NG9).

  • Royal College of Paediatrics and Child Health (RCPCH). Bronchiolitis clinical resources.

  • JCVI. Advice on RSV immunisation for infants (nirsevimab and maternal Abrysvo programmes).

  • MHRA. Nirsevimab (Beyfortus) product information.

  • UK Health Security Agency (UKHSA). RSV surveillance and green book chapter 27a.

Red flags

When bronchiolitis needs urgent attention.

Most infants manage safely at home. These are the situations that do not, and where a hospital opinion is essential.

  • Apnoea

    Any pause in breathing, especially in infants under six weeks or premature babies, is a reason for immediate hospital review.

  • Oxygen saturation below 92%

    A persistent SpO2 under ninety-two per cent in air is an admission threshold under NICE NG9.

  • Poor feeding or dehydration

    Taking under half of normal feeds, fewer than three wet nappies in twenty-four hours, or a sunken fontanelle needs urgent assessment.

  • Severe respiratory distress

    Marked recessions, tracheal tug, grunting or exhaustion means the infant is struggling and needs to be seen the same day.

  • Cyanosis or a silent chest

    Blue lips or tongue, or a chest that has become quiet, are emergencies. Call 999.

  • Young age or high-risk background

    Age under twelve weeks, prematurity, congenital heart or lung disease, or immunocompromise all lower the threshold for admission.

  • Parental concern about a floppy baby

    A carer who says the baby is not themselves, is floppy or difficult to rouse should always be taken seriously.

  • Failure to improve after seven to ten days

    Most infants turn a corner within a week. Ongoing worsening warrants a chest X-ray and paediatric review.

  • Fever in an infant under three months

    Any temperature above thirty-eight degrees in a baby under three months needs urgent assessment, including a urine culture.

Living with it

A short illness with a long tail of coughing.

Four things that make the biggest difference at home. Feeding little and often, watching breathing carefully, being patient with a lingering cough and taking up prevention when it is offered.

A quiet reminder

Trust your instincts as a parent.

If your baby is not themselves, is working harder to breathe or is feeding much less, ask for a review. It is always better to be seen and reassured.

  1. 01 At home

    Small, frequent feeds

    Offer smaller feeds more often, keep the baby upright and use saline drops with gentle suction before feeds and sleep.

  2. 02 Watching

    Know the warning signs

    Count breaths, look at the chest wall and check wet nappies. If breathing quickens, feeding drops or colour changes, seek help.

  3. 03 Recovery

    A cough that lingers

    Cough can last two to four weeks after the acute illness. It is not a sign that treatment has failed.

  4. 04 Prevention

    Ask about nirsevimab

    Since 2024, most UK infants under twelve months are eligible for a single dose of nirsevimab before their first RSV season. Ask your midwife, GP or health visitor.

Frequently asked

Everything parents ask us about bronchiolitis.

Quick answers on RSV, warning signs, treatment and the newer prevention options.

  • What is bronchiolitis?

    A viral lower respiratory tract infection in infants under two years, most often caused by respiratory syncytial virus (RSV). It inflames the smallest airways in the lungs and causes cough, wheeze, fast breathing and feeding difficulty. It peaks between three and six months of age and is a winter illness in the UK, running from November to March.

  • How is it different from a cold or asthma?

    It starts like a cold with coryza and mild fever, but after two or three days moves down into the chest with wheeze, crackles and increased work of breathing. Unlike asthma, it does not respond to inhalers or steroids. NICE NG9 specifically advises against routine use of bronchodilators, steroids and antibiotics in bronchiolitis.

  • When should I take my baby to hospital?

    Call 999 or go straight to A&E if your baby has pauses in breathing, is blue around the lips, is grunting, is exhausted or floppy. Contact 111 or your GP the same day if breathing is fast, chest recession is marked, feeds are under half of normal, wet nappies have dropped, or your baby is under three months and has a fever.

  • Do antibiotics help?

    No. Bronchiolitis is caused by viruses and antibiotics do not work against them. NICE does not recommend antibiotics unless there is clear evidence of a bacterial infection on top, which is uncommon. Overuse of antibiotics causes side effects and drives resistance without helping the baby recover.

  • What is nirsevimab and can my baby have it?

    Nirsevimab (brand name Beyfortus) is a long-acting monoclonal antibody given as a single injection that protects infants against RSV for a whole season. The JCVI recommended universal infant use in 2024 and the UK is rolling it out through NHS programmes. Most babies born before or during the RSV season are eligible. Ask your midwife, GP or health visitor about the local programme.

  • Should I have the RSV vaccine in pregnancy?

    The Abrysvo vaccine is offered on the NHS from twenty-eight weeks of pregnancy and protects newborns for the first six months of life by passing antibodies across the placenta. It is safe in pregnancy and reduces the risk of severe bronchiolitis in infants. It is offered alongside, or as an alternative to, nirsevimab after birth depending on your local pathway.

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