RSV circulates in the UK every winter, typically starting in October and peaking in December or January.
The virus, which mostly affects young children, is normally mild. But it can develop into a more serious illness and require hospital treatment.
During the past two winters, cases were higher than usual after pandemic measures in previous years suppressed cases – meaning children had much lower immunity.
Here is what you need to know.
What is RSV?
RSV is short for respiratory syncytial virus.
It is a very common virus and most children will have had it by the time they are two.
However, it can reinfect older children and adults may also catch it. Older adults are particularly at risk of complications.
What are the symptoms of RSV?
Most children infected with RSV will only experience mild symptoms, including:
• runny nose
• decrease in appetite
• coughing
• sneezing
• fever
• wheezing
These symptoms usually come in stages, rather than all at once. In very young children, the only symptoms may be irritability, decreased activity, and breathing difficulties.
What are the possible complications?
RSV can cause a chest infection called bronchiolitis, which mainly affects children under two.
It is usually mild and can be treated at home, according to the NHS, but it can be serious.
Bronchiolitis is not the same as bronchitis, which causes a cough with lots of mucus and can affect people of all ages.
The symptoms of bronchiolitis include:
• breathing more quickly
• finding it difficult to feed or eat
• noisy breathing (wheezing)
• becoming irritable
Symptoms are usually worst between days three and five, and the cough usually gets better in three weeks, the NHS says.
Some children have a higher risk of getting seriously ill with bronchiolitis, including children born very prematurely, those with a heart or lung condition or a weakened immune system.
About 3 in 100 babies with bronchiolitis will need hospital treatment, according to Asthma + Lung UK.
RSV results in 20 to 30 infant deaths per year in the UK, according to the Department of Health and Social Care.
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When should you seek treatment?
The NHS advises parents to call 999 or go to A&E if any of the following happens:
• your child is having difficulty breathing – you may notice grunting noises or their tummy sucking under their ribs
• there are pauses when your child breathes
• your child’s skin, tongue or lips are blue
• your child is floppy and will not wake up or stay awake.
Parents should ask for an urgent GP appointment or call 111 if any of the following happens:
• your child has had a cold and it’s getting worse
• your child is feeding or eating much less than normal
• your child has had a dry nappy for 12 hours or more, or shows other signs of dehydration
• your baby is under 3 months and has a temperature of 38C or more, or is older than 3 months and has a temperature of 39C or higher
• your baby feels hotter than usual when you touch their back or chest, or feels sweaty
• your child is very tired or irritable.
What treatment is available?
There is no specific treatment for RSV and instead treatment is aimed at relieving symptoms.
The anti-viral drug ribavirin has been licensed for treating RSV and is sometimes used in severe cases, but its effectiveness has not been established.
At home, symptoms of RSV and bronchiolitis can be treated with child paracetamol or ibuprofen. Saline nasal drops may make it easier for them to breathe, and feeding babies upright can also help.
In hospital, a child with bronchiolitis may be given extra oxygen. If they are struggling to feed, they may be given food or fluids through a feeding tube. They may also be treated with nasal suction to get rid of excess mucus in the nostrils.
Is there a vaccine?
A vaccine to prevent RSV in infants and toddlers, Beyfortus (nirsevimab), was approved by the UK’s medicines regulator in November 2022.
The Medicines and Healthcare products Regulatory Agency (MHRA) also approved a vaccine, Arexvy, for people over 60 in July.
But the vaccines are not yet available as part of a national immunisation programme.
The Joint Committee on Vaccination and Immunisation (JCVI) said in June that a cost-effective RSV immunisation programme should be developed for infants and older adults – but there was no timeline for when it might be brought in.