What is the RSV virus and why is it surging among children?

The RSV infection may join forces with Covid and flu to form a “triple threat” of respiratory viruses that “could collide this winter”, experts believe.

If seasonal diseases like influenza and RSV were to coincide with another large wave of Covid, we “could be facing a public health disaster” in the form of a “tripledemic”, warned Adam Kleczkowski, professor of mathematics and statistics at the University of Strathclyde, on The Conversation.

What is RSV?

A common winter virus, RSV – or respiratory syncytial virus – usually causes mild coughs and colds but occasionally results in serious infections like bronchiolitis and pneumonia, particularly in young children. The elderly are also at particular risk.

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The symptoms are “similar to a cold”, said the UK Health Security Agency. They might include:

• a runny nose
• sneezing
• nasal congestion
• a cough
• a fever
• ear infections

“Every year, about 29,000 babies need hospital care for RSV and most have no other health issues beforehand,” said the BBC.

It can spread in households because children “commonly get RSV at school or day care and bring it home to other family members”, said CNET, but most adults will “either have mild or no symptoms of RSV”.

Why is RSV on the rise?

In short, measures taken to stop Covid also led to a reduction in the spread of other viruses and we are all now less immune. Following a “hiatus” in 2020-21, noted Kleczkowski, the “seasonal pattern seems to be returning”, but this autumn has “already seen high hospitalisation numbers”.

“At the beginning of the pandemic, we took all these behavioral measures to tamp down on Covid transmission,” Katherine Wu, science writer for The Atlantic, told Slate, which “also happened to work marvellously against all these other respiratory viruses”.

But those viruses, including RSV, have now “taken every opportunity to come back”, she explained, and hit kids who “didn’t have the opportunity to be exposed to these viruses during the pandemic and build up the immunity that might have dampened the severity of their first infections”.

So what can be done about it?

A new treatment to protect babies has been approved by the UK regulator. The antibody treatment, called nirsevimab and made by AstraZeneca and Sanofi, has been shown to reduce lower respiratory tract infections caused by RSV by 74.5% in trials involving 4,000 babies.

“It works by preventing RSV from fusing to cells in the respiratory tract and causing infections,” explained the BBC, but “it still needs more research in larger numbers of babies before it can be used on the NHS”.

To that end, researchers who hope to determine whether it can cut the number of babies needing hospital care for RSV are calling for parents of newborn babies and those up to 12 months old to sign up for a study.

A vaccine against RSV made by Pfizer has produced promising results in trials. It was found that, when given to pregnant women to protect their newborns, it was 81% effective against severe respiratory illness because of RSV in the first 90 days of a baby’s life, said the BBC.