RSV in Babies: Symptoms, Red Flags & Bronchiolitis

Your baby got a runny nose, and a couple of days later they're breathing fast, wheezing, and barely taking the breast or bottle. The doctor says: "It's bronchiolitis, most likely RSV." It sounds frightening — and the first thing you want to know is whether this is still just a cold or already something serious. In this article we'll go through what bronchiolitis is, how RSV symptoms in infants differ from an ordinary cold, which signs mean "go to the hospital right now," what genuinely helps at home (and what's useless or harmful), and how to protect your baby.

What is bronchiolitis, and where does RSV come in?

Bronchiolitis is inflammation of the smallest airways in the lungs (the bronchioles). In babies under a year old, these tubes are extremely narrow — less than a millimetre across. When their walls swell and mucus builds up inside, the opening narrows even further, and air struggles to get through. That's where the whistling, the rattling and the fast breathing come from. In an adult, the very same virus would cause nothing more than a runny nose and a cough.

The main cause of bronchiolitis is respiratory syncytial virus (RSV). It's behind most cases; less often the culprit is rhinovirus, human metapneumovirus, flu, adenovirus or a common coronavirus. This isn't some rare exotic illness: according to the WHO and the CDC, virtually every child catches RSV at least once by the age of two. For most, it plays out as a regular cold, and only in some babies does it travel lower down into the bronchioles.

It mainly affects children under 2, and it hits babies in their first 6 months hardest. In the northern hemisphere the season usually runs through the cooler months — roughly from late autumn to early spring, peaking in winter — although the timing shifts from region to region.

How RSV in babies unfolds, day by day

Bronchiolitis follows a fairly recognisable script, and knowing it takes a lot of the fear away:

• Days 1–2. It all looks like a common cold: a heavy clear runny nose, sneezing, sometimes a mild fever, a light cough.
• Days 3–5. The cough gets worse, wheezy or "noisy" breathing appears, the breathing rate goes up, and your baby tires quickly at the breast. This is the peak — the hardest days are usually the third to the fifth. This window is when a check-up with a doctor is most often needed.
• Days 5–7 and beyond. Breathing gradually settles, appetite returns, and your baby starts to seem like themselves again.
• Weeks 2–4. A leftover cough can hang around for another 2–4 weeks, sometimes longer. That's normal and doesn't by itself mean the treatment failed — the tiny hairs (cilia) lining the airways take a while to recover.

Symptoms often seem worse at night and in the early morning: lying flat makes mucus harder to clear and the nose blocks up faster. Your baby may wake more often and sleep poorly — this is temporary, and once breathing eases, sleep usually recovers on its own (unlike the age-related sleep regressions, which have nothing to do with illness).

Bronchiolitis signs vs. an ordinary cold

The difference isn't the runny nose — that's there either way. The difference is in breathing and feeding. With a plain cold your baby snuffles through their nose but breathes calmly and feeds almost as usual. With bronchiolitis, the "work of breathing" kicks in.

Wheezing and noisy breathing in an infant

Parents describe it in different ways: "whistling," "rattling," "puffing," "breathing like a little steam engine." The sound is usually clearest on the out-breath. It's worth telling apart noisy snuffling from the nose (the sound comes from "up top" and disappears once you clear the nose) and wheezing from the chest (the sound stays; put a hand on the chest and you can often feel a vibration). The second one is a reason to have your baby seen by a doctor.

How to spot fast or laboured breathing

Count your baby's breaths when they're calm or asleep: a full minute, watching the rise of the chest or tummy. The WHO's cut-offs for "fast breathing" are:

• under 2 months — 60 breaths per minute or more;
• 2–11 months — 50 or more;
• 1–5 years — 40 or more.

Don't count during crying or straight after a feed — the number will be falsely high.

Trouble with feeding

A baby can't breathe fast and suck at the same time. So they take a few swallows, pull off, catch their breath, get frustrated, tire out and fall asleep hungry. If your baby is taking less than half to three-quarters of their usual amount across several feeds in a row, that's an important signal — not because they're being fussy, but because breathing is using up all their energy. If you're breastfeeding, short frequent feeds are a lifesaver on days like these — we covered feeding routines in more detail in our article on how to get breastfeeding off to a good start.

Red flags: when your baby needs help urgently

This is the most important part. Call emergency services immediately if your baby has:

• a blue or grey tinge to the lips, tongue or face;
• pauses in breathing (apnoea) — especially in babies in their first months and those born preterm;
• is very hard to wake, is floppy, listless, or not responding the way they normally do;
• breathing that has become not fast but weak and slow, as if the baby is "too tired to breathe."

See a doctor the same day if you notice:

• retractions — the skin pulling in between the ribs, under the ribs, or in the hollow above the breastbone with every breath;
• nostrils flaring on the in-breath;
• a grunting sound on the out-breath;
• a breathing rate above the cut-offs listed earlier while your baby is calm;
• your baby is taking less than half their usual feeds, is producing fewer wet diapers (for example, none in 8–12 hours), has a dry mouth, or cries without tears;
• a temperature of 38 °C (100.4 °F) or higher in a baby under 3 months — that always warrants urgent assessment, no matter how well the baby seems;
• you simply feel your baby is noticeably worse. Parental worry is a valid reason, and clinicians take it seriously.

Judge by the overall picture rather than a single symptom: how your baby breathes, how they feed, and how they look between coughing fits.

Which babies are at higher risk

Most children get through bronchiolitis at home. But severe illness and hospital admission are more common in babies who:

• were born preterm;
• are under 2–3 months old when they catch it;
• have a congenital heart defect or chronic lung disease (bronchopulmonary dysplasia, for example);
• have a weakened immune system (a congenital immunodeficiency, or treatment that suppresses immunity);
• live with neuromuscular conditions that make coughing things up difficult;
• are regularly exposed to tobacco smoke.

If your baby is in one of these groups, it's worth contacting your doctor early — at the first signs of laboured breathing, rather than waiting for red flags.

RSV treatment at home: what actually helps

There's no specific "bronchiolitis medicine": the body clears the virus itself, and our job is to support the baby while it does. Here's what works:

• Fluids and frequent small feeds. Feed more often but in smaller amounts — that makes it easier to combine eating and breathing. Breastfeeding is especially valuable during illness: milk provides both fluid and protection.
• Saline drops and gentle suctioning. A couple of drops of saline in each nostril 10–15 minutes before a feed, then careful suction with a nasal aspirator or bulb syringe. A clear nose usually brings the most noticeable relief — young babies breathe mainly through the nose. Don't overdo it, though: suctioning too often irritates the lining.
• A more upright position while awake. Holding your baby upright or semi-upright when they're awake often makes breathing easier. For sleep, though, they should still be on their back on a firm flat surface, with no pillows and nothing propped under the mattress — tilting the head of the crib isn't recommended because of the risk of sliding down and suffocating.
• Bringing a fever down with an age-appropriate fever reducer — the specific medicine, form and dose should only be chosen by your doctor or pharmacist, based on age and weight.
• Moist, cool, clean air and absolutely no tobacco smoke in the house.
• Monitoring. Recount the breathing rate every few hours, count wet diapers, and note how much your baby has eaten. These simple numbers are genuinely useful to a doctor.

What doesn't help — and what can harm

• Antibiotics. Bronchiolitis is caused by a virus, and antibiotics do nothing to it. They're prescribed only for a confirmed bacterial infection — and that's a doctor's call.
• Bronchodilators (albuterol/salbutamol and similar) and inhaled or systemic steroids. Clinical bronchiolitis guidelines, including the American Academy of Pediatrics guideline, advise against using them routinely: in most infants they don't improve the course of the illness.
• Over-the-counter cough and cold syrups. They're not safe for young children and don't shorten the illness.
• Honey is not allowed under 1 year because of the risk of botulism.
• Camphor and essential-oil rubs, turpentine, mustard plasters and steam inhalations — these risk irritating the airways and causing burns.
• X-rays and blood tests "just in case" usually aren't needed in a typical case — the diagnosis is made on examination.

The crying and unsettledness of a sick baby is easy to confuse with other causes, and vice versa. If a bloated tummy and evening crying show up without any breathing trouble, that may be a different story altogether — we looked at it in our article on colic in newborns.

How bronchiolitis is treated in hospital

Only a minority of babies need admission, and the treatment there is supportive too — just with tools you don't have at home:

• oxygen, if blood oxygen levels drop;
• feeding support — expressed milk or formula through a tube, and an IV drip if needed;
• high-flow nasal therapy (a warm, humidified flow of air with oxygen) if breathing is hard work; in rare severe cases, more advanced respiratory support;
• monitoring of breathing and oxygen saturation.

There's no specific antiviral drug for a typical case of RSV bronchiolitis. Most babies admitted to hospital spend a few days there and recover fully.

Prevention: what genuinely lowers the risk

The RSV infant immunisation and the maternal RSV vaccine

In recent years, two real tools for protecting infants have become available:

• Nirsevimab — a long-acting monoclonal antibody. It isn't a vaccine: it gives your baby ready-made protective antibodies and is given as a single dose before the RSV season or shortly after birth. In trials and in practice it markedly reduces doctor visits and hospital admissions for RSV lower-respiratory infection.
• The RSV vaccine in pregnancy. Given within a specific window of pregnancy, it lets you pass maternal antibodies to your baby through the placenta, protecting them through the first months of life — when the risk is highest.

Both approaches are recommended in a growing number of countries, but availability, timing and schedules differ. Check with your doctor or your local immunisation service about what's offered where you live and whether it's right for you or your baby — there's no single universal schedule here. If you're pregnant and discussing respiratory infections with your provider, our article on colds and flu during pregnancy may also be useful.

Simple everyday measures

• wash your hands before picking up your baby — and ask visitors to do the same;
• keep people with cold symptoms away from your baby where you can, including older siblings; kissing a newborn on the face during the season isn't the best idea;
• regularly wipe down surfaces and the toys that go into your baby's mouth;
• ban smoking entirely in the house and the car;
• breastfeed if you can — breastfeeding is linked to milder respiratory infections;
• where possible, avoid taking a young baby into crowded places at the peak of the season.

Frequently asked questions

How long does bronchiolitis last?

The acute phase lasts roughly 7–10 days, peaking on days 3–5. The cough may linger for another 2–4 weeks, gradually fading.

Can a baby get bronchiolitis more than once?

Yes. Immunity to RSV is incomplete and short-lived, so reinfections do happen — but they're usually milder each time.

Is RSV contagious, and how does it spread?

Very contagious. It spreads in droplets from coughing and sneezing, and also via hands and surfaces: the virus can survive on objects for several hours. A child is usually infectious for about 3–8 days, sometimes longer.

Does having bronchiolitis mean my child will get asthma?

No, it doesn't. Some children have repeated episodes of wheezing with colds in the years after bronchiolitis, and that link is still being studied — but having had bronchiolitis is not the same as a diagnosis of asthma.

Do saline nebuliser treatments help?

At home, in a typical case of bronchiolitis, a nebuliser usually isn't needed; hypertonic saline is sometimes used in hospital. The decision about nebulised treatments belongs to a doctor, not to advice from a parents' group chat.

Key takeaways

• Bronchiolitis is inflammation of the tiniest airways, most often caused by RSV; nearly every child has it by the age of 2, and babies in their first months have the hardest time.
• What separates it from a cold isn't the runny nose but breathing and feeding: wheezing from the chest, fast breathing, retractions, refusing feeds.
• The worst days are 3–5, and the cough can drag on for weeks after recovery.
• Call emergency services immediately for blue lips or face, pauses in breathing, or marked listlessness; see a doctor the same day for retractions, grunting, flaring nostrils, dehydration, or a temperature of 38 °C (100.4 °F) in a baby under 3 months.
• At home, what works is frequent small feeds, saline drops and nose clearing, an upright position while awake, and monitoring. Antibiotics, bronchodilators, steroids, cough syrups and honey under 1 year either don't work or are unsafe.
• For prevention, talk to your doctor about nirsevimab for your baby and the RSV vaccine in pregnancy — availability depends on your country — plus hand hygiene, a smoke-free home and breastfeeding.

This article is general information and does not replace personalised medical advice. If you're worried about your baby's breathing or how they're doing, contact your pediatrician or seek urgent care.