Bronchiolitis is almost always caused by a viral infection. In most cases, the respiratory syncytial virus (RSV) is responsible.
RSV is a very common virus and almost all children are infected with it by the time they're 2 years old.
In older children and adults, RSV may cause a cough or cold, but in young children it can cause bronchiolitis.
Most cases of bronchiolitis are not serious, but parents and carers should contact their GP or call freephone NHS 111 if:
- You’re worried about your child
- Your child has taken less than half their usual amount during the last 2 or 3 feeds, or they have had a dry nappy for 12 hours or more
- Your child has a persistent high temperature of 38C or above
- your child seems very tired or irritable.
Parents and carers are also advised to dial 999 for an ambulance if:
- Your baby is having difficulty breathing.
- Your baby's tongue or lips are blue.
- There are long pauses in your baby's breathing.
Medical professionals can find a poster HERE to download, print and distribute where necessary.
How the infection is spread
Viruses are spread when an infected person coughs or sneezes.
Tiny droplets of liquid can be breathed in directly from the air or picked up from a surface they have landed on, such as a toy or table.
For example, your child can become infected after touching a toy that has the virus on it and then touching their eyes, mouth or nose.
RSV can survive on a surface for up to 24 hours.
An infected child can remain infectious for up to 3 weeks, even after their symptoms have disappeared.
How it affects the lungs
Once you become infected, the virus enters the respiratory system through the windpipe (trachea).
The virus makes its way down to the smallest airways in the lungs (the bronchioles).
The infection causes the bronchioles to become inflamed (swollen) and increases the production of mucus.
The mucus and swollen bronchioles can block the airways, making breathing difficult.
As babies and young children have small, underdeveloped airways, they're more likely to get bronchiolitis.
Who's most at risk?
Bronchiolitis is very common in infants and is usually mild.
Several things can increase a child's likelihood of developing the infection.
- being breastfed for less than 2 months, or not at all
- being exposed to smoke (for example, if parents smoke)
- having brothers or sisters who attend school or nursery, as they're more likely to come into contact with a virus and pass it on
There are also a number of factors that can increase the risk of a child developing more severe bronchiolitis.
- being under 2 months of age
- having congenital heart disease
- being born prematurely (before week 37 of pregnancy)
- having chronic lung disease of prematurity (when injury to the lungs causes long-term respiratory problems in premature babies)
RSV and COVID-19
Babies born since the COVID-19 pandemic have not had as much exposure to common viruses which would build up their immune system. As measures such as social distancing and mask wearing are relaxed, Public Health England are expecting to see an increase in cases this season.