A contagious virus that poses a particular threat to children has sparked concerns over a potential 'tripledemic' this winter.
Our health service is already braced for a 'twindemic' of rising flu cases and a potential resurgence of Covid in the coming months.
But now an expert says there's a third prevalent illness to worry about - the common respiratory syncytial virus (RSV), which usually causes mild, cold-like symptoms.
Fortunately it doesn't tend to present a serious problem, but it can cause pneumonia and swelling of the airwaves in babies, the elderly, and vulnerable people.
Most people recover in a week or two, but RSV can be serious, particularly for infants and older adults.
It is the leading cause of infant hospitalisations in the UK and close to a third of under-fives with respiratory symptoms swabbed as part of UK Health Security Agency (UKHSA) surveillance test positive.
High vaccination levels have meant that large swathes of the population are well protected from flu and Covid - but these two viruses don't usually cause severe illness in young people, unlike RSV.
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Professor Francois Balloux, director at the UCL Genetics Institute, told Express.co.uk : "RSV is a leading cause of child hospitalisation and the virus kills more than 100,000 children each year globally. That’s more than 50 times as many children than those who died from Covid throughout the pandemic.
"It’s a far bigger threat to young children than Covid or seasonal flu."
He continued: "RSV is highly contagious and the majority of children experience an RSV infection before the age of two. It’s not obvious that its spread can be suppressed without enforcing highly disruptive measures. There is hope RSV child hospitalisations and deaths will decrease in the future with new RSV vaccines being rolled out soon."
UKHSA's recent figures show nearly a third of under-fives currently have RSV. This comes at the same time as flu levels have spiralled higher than normal after two years of lockdown, while more than two million people in the UK have Covid.
This has, of course, sparked fears of a 'tripledemic' - but an expert has been quick to dispel any worry.
Professor Amitava Banerjee, from the Institute of Health Informatics and UCL, said: "In my view the word 'tripledemic' is just the latest soundbite and we do not necessarily know that RSV will be as big a threat.
"I think far greater potential threats to the NHS is due to chronic underfunding, chronic understaffing and the indirect and long-term effects of Covid."
But this hasn't stopped parents from getting worried about the potential number of RSV cases this winter.
Victoria Fuller, a mum-of-one, told the Express: "My daughter has had five bugs in the space of eight weeks - at least three of those have been of the respiratory kind.
"It's a scary time for parents who are trying to be vigilant against these extra illnesses going around, but at the same time, life has to go on. No nursery would mean no work for me - and with the cost of living crisis well underway, that's just not an option."
Speaking about the tripledemic threat, Emeritus Professor Ron Eccles told the Daily Mail : "When lots of people get ill at the same time, and particularly during the winter, the pressure on health services can be very intense."