RSV and bronchiolitis: what parents need to know and the danger signs
Last updated September 3, 2026.
RSV is so common that nearly all children catch it by age two, and in most it is just a cold; in young babies it can become bronchiolitis, where the small airways swell and breathing and feeding get hard. The typical course: a runny nose and slight fever, then a cough, then a day or two where breathing is the hard work. It usually peaks around days 3 to 5 of the cough and most babies recover fully in two to three weeks with home care. The whole game is watching the breathing and the feeding.
What does bronchiolitis look like?
A cold first: runny nose, sneezing, mild fever. Then a dry, sometimes wheezy cough, breathing that is faster or harder than normal (you may see the skin pulling in between or below the ribs or at the throat), and feeding that falls off because breathing through a blocked little nose while sucking is exhausting. Babies often manage smaller feeds more frequently. A rasping, crackly, or wheezy chest is common. The cough can linger for three weeks even in a child who is otherwise recovering; that is normal healing, not deterioration.
What actually helps?
- Smaller feeds, more often: breathing takes priority over a full bottle, so offer half-size feeds at twice the frequency. Watch wet nappies: fewer than about half the usual number means they are not getting enough fluid.
- Clear the nose before feeds and sleep: saline nose drops from the pharmacy, one in each nostril before feeds, genuinely help a snuffly baby feed. Keep them upright as much as possible; flat lying makes breathing harder.
- Fever and comfort: paracetamol or ibuprofen dosed by weight (ibuprofen only over 3 months) for fever and obvious discomfort.
- Smoke-free, absolutely: cigarette smoke worsens bronchiolitis and raises the risk of it becoming severe. No smoking anywhere near the baby, including clothing that smells of smoke.
- What does not help: antibiotics (RSV is viral), cough medicines (not for babies), and steam. There is no home medication that shortens bronchiolitis; your job is feeding, fluids, and watching the breathing.
When is it an emergency?
Call 999 (or 911/112) if your baby: has pauses in breathing longer than about 10 seconds, turns blue or very pale, especially around the lips and tongue, is breathing very fast with marked pulling in at the ribs or throat and cannot feed, is floppy or unresponsive, or is a young infant with worsening exhaustion from the work of breathing. Same-day urgent care for feeding that has dropped to under half of normal, dry nappies over a day, a fever in a baby under 12 weeks, or anything that tells your gut this is more than a cold. Premature babies and those with heart or lung conditions have a lower threshold for hospital from the start. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
What is the difference between RSV and bronchiolitis?
RSV is the virus; bronchiolitis is the illness it causes when it reaches the small airways (bronchioles) of young babies. RSV stands for respiratory syncytial virus, and almost all children catch it by their second birthday. In older children and adults it is a cold. In babies under a year, especially under 3 months, the swelling and mucus in their tiny airways make breathing and feeding genuinely hard, and that is bronchiolitis. Most bronchiolitis is caused by RSV.
How long does bronchiolitis last?
The breathing difficulty typically peaks around days 3 to 5 of the cough and then eases, with most babies back to feeding and breathing comfortably within two to three weeks. The cough itself can linger up to three weeks without meaning anything is wrong. The trend is what matters: day-by-day improvement in feeding and breathing effort after the peak, not instant silence of the cough. A baby who is getting worse after the first week instead of better needs review.
How do I care for my baby with bronchiolitis at home?
Feed smaller amounts more often, because breathless babies cannot finish full feeds. Use saline nose drops before feeds to clear the nose. Keep your baby upright as much as practical, and slightly raised for sleep in the cot (no pillows or positioners). Give paracetamol or ibuprofen by weight for fever and discomfort. Keep the air smoke-free and the room comfortably cool. Watch two numbers through the day: how much they are feeding, and how hard the breathing looks. Both guide whether home care is still the right level.
Why are some babies at higher risk from RSV?
The smallest airways struggle most: babies under 3 months, premature babies, and those born with heart or lung conditions are the groups more likely to need hospital care. Exposure to cigarette smoke raises risk and severity, and not being breastfed removes some protection. For high-risk babies there is a preventive antibody injection given through RSV season in many countries, and an RSV vaccine offered in pregnancy; ask your midwife or doctor what applies where you live.
When should I take my baby to hospital for bronchiolitis?
Call an ambulance for: pauses in breathing longer than about 10 seconds, blue or very pale lips or tongue, severe breathing difficulty with marked pulling in of the chest, floppiness or unresponsiveness, or obvious exhaustion from breathing. Go the same day for: feeding under half of normal, dry nappies across a day, fever in a baby under 12 weeks, worsening chest indrawing, or your instinct saying this is escalating. Hospitals see bronchiolitic babies constantly and would always rather check a baby who turns out fine.
Does bronchiolitis cause asthma later?
There is an association: children who had bronchiolitis, especially severe or repeated episodes, are more likely to wheeze with viruses in the following years and are diagnosed with asthma more often. Whether bronchiolitis causes that or simply marks children already prone to it is unsettled. The practical takeaway is not to worry about a single typical episode, but to mention the bronchiolitis history if your child later wheezes with colds, because it shapes how those episodes get managed.
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