What Is RSV and How Do You Protect Your Little One?

A Little Rei newborn set for 0 to 6 months

I've sat up with two of my own through a bad chest. I'm not a clinician, and everything below defers to your doctor, and the section on the signs that mean go now is the one to read before you need it. Respiratory syncytial virus is so common that essentially every child has had it by two, and in an adult it presents as an ordinary cold. In a baby under one, particularly under six months, it can move into the smallest airways and cause bronchiolitis, which is the most frequent reason infants are admitted to hospital. Most babies who get it are fine at home in a week or two, while the small proportion who aren't tend to deteriorate on day three to five, and the signs are specific enough to watch for.

This post isn't medical advice

This is written to help you recognise what you're looking at and ask better questions. If your baby is unwell, contact a doctor. If any of the urgent signs below are present, seek emergency care immediately and stop reading.

What it looks like

It starts as an unremarkable cold and changes character after a couple of days.

Days 1-2: runny nose, mild cough, sometimes a temperature. Indistinguishable from any other cold.
Days 3-5: the cough worsens, breathing becomes faster, feeding slows, and there may be wheezing or a crackling sound. This is the window where infants get worse.
Days 5-7: usually the turning point, with breathing settling first.
Weeks 2-4: the cough often lingers well after everything else has resolved. That alone isn't a cause for concern.

A good non-obvious signal in small babies is feeding. A baby taking well under half her normal intake is telling you her breathing is taking too much effort to feed properly. Infants can't easily breathe hard and feed at the same time.

Through the season

The signs that mean get help now

Call emergency services or go to an emergency department if you see any of these.

Pauses in breathing, or breathing that stops briefly. In very young babies this can be the first serious sign.
Working hard to breathe: the skin sucking in under the ribs or at the base of the throat, nostrils flaring, or the abdomen pulling in with each breath.
A grunting noise at the end of each breath.
Blue or grey lips, tongue or face; pale, mottled or unusually cold skin.
Very difficult to wake, floppy, or not responding as they normally would.
Under half of normal feeds over 24 hours, or no wet nappy for 12 hours.
A baby under three months with a temperature of 38°C or above.

Contact a doctor the same day, without waiting, for breathing that's faster than usual, a worsening cough with reduced feeding, a temperature over 38°C in a young infant, or any sense that your baby is deteriorating. Parental concern that a child isn't themselves is treated as a warning sign in clinical guidance for good reason.

What helps at home

There's no treatment that shortens RSV. Antibiotics don't work on it. It's a virus. Care is supportive, and the aim is comfortable breathing and adequate fluid.

Feed little and often. Smaller, more frequent feeds are far easier for a blocked, breathless baby than full ones.
Clear the nose before feeds. Saline drops and a gentle aspirator make a real difference, because babies breathe through the nose.
Keep them upright when awake, and hold them for feeds and not lying flat. For sleep, still on the back on a flat surface, don't prop the cot or use a wedge.
Watch nappies. Output is the simplest hydration check you have.
Paracetamol or ibuprofen for discomfort or fever, at the correct dose for age and weight, if advised.
Skip cough medicines, but they aren't recommended for young children and don't help bronchiolitis.

Reducing the risk

You can't avoid RSV. What you can change is when they meet it and how much they get.

Immunisation, and this is the part that has changed, and there are now two routes: a vaccine given in pregnancy, which passes protection to the baby, and a long-acting antibody injection given to infants. In the MELODY trial, that antibody injection cut medically attended RSV lower respiratory infection by 74.5% across 1,490 healthy late-preterm and term babies. Availability and eligibility vary by country; ask your doctor which applies where you are.
Hand washing, relentlessly, especially before holding a newborn. RSV spreads by droplets and by surfaces, and it survives on hard surfaces for hours.
Keep unwell visitors away from a young baby, and be willing to say so. A cold in an adult is bronchiolitis in a newborn.
No smoking anywhere near the baby, including on clothes. Tobacco smoke exposure meaningfully increases the risk of severe disease.
Breastfeed if you can. It lowers the risk of severe infection.
Be cautious with crowds and shared indoor spaces in the first months, particularly during local RSV season.

Who's at higher risk

For most babies this is a bad cold. For these, the threshold for seeking help is lower. Where exactly it lies I'm not certain anybody can say, so I'd err early.

Babies under six months, and especially under three.
Babies born prematurely.
Babies with congenital heart disease or chronic lung disease.
Babies with a weakened immune system or significant neuromuscular conditions.

If your baby is in one of these groups, ask your doctor in advance what their threshold for review should be, so that you aren't working it out during a bad night. A plan agreed beforehand is a great help at 2am, and I'd add that the monoclonal antibody options for infants have changed since 2023, so ask what's available here this season. I don't keep up with it well enough to say.

Evidence

This guide is general information, written to help you understand a topic and ask better questions. It is not medical advice and does not replace your own doctor, midwife or paediatrician. Anything that worries you about your baby belongs with them.

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