HEALTH bosses have warned of a surge in a super common bug that can cause dangerous lung infections - amid fears of a winter "tripledemic".
An uptick in RSV infections has seen more babies admitted to hospital with severe chest infections, the UK Health Security Agency (UKHSA) said.
RSV stands for respiratory syncytial virus - it's a common and contagious group of viruses that's behind many childhood coughs and colds.
In fact, most children will get an infection caused by RSV before the age of two.
The bug can cause a chest infection called bronchiolitis.
Most tots will only get cold-like symptoms and a slightly high temperature from the infection, but they can also start wheezing and breathing more quickly.
In some cases, bronchiolitis can turn serious, causing breathing difficulties that will need to be treated in hospital.
UKHSA said more babies had been taken to hospital with a serious chest infection in the week leading up to October 10.
Dr Conall Watson, consultant epidemiologist at UKHSA, said: "We are beginning to see cases of RSV increasing, as well as emergency department attendances for acute bronchiolitis, caused by RSV."
According to the health watchdog, emergency department attendances for acute bronchiolitis have increased across the country.
It comes amid warnings of looming a winter "tripledemic" caused by "colliding" surges of Covid, flu and RSV.
The NHS rolled out a vital jab that protects against RSV infections just a few months ago.
It's being offered to pregnant women to help pass on protection to their babies against RSV and illnesses like bronchiolitis.
Expectant mums have been invited to book a free jab once they reach 28 weeks.
Having the vaccine in week 28 or within a few weeks of this will help build a good level of antibodies to pass on to their baby before birth, UKHSA noted.
Newborn babies will receive protection from the bug this way, even if they are born early.
The jab is also being offered to older adults, as they can be vulnerable to severe illness from RSV infections too.
Dr Watson said: "RSV lung infections like bronchiolitis are a major cause of babies needing to visit A&E or be admitted to hospital each winter.
"The RSV vaccine in pregnancy is an important step in keeping babies well.
"Women who are 28 or more weeks pregnant should take it up now, along with people aged 75-79 years who are also offered the vaccine by the NHS as part of the new programmes."
The epidemiologist shared key warning signs indicating your baby might need hospital treatment for a lung infection.
"If your baby has a cold that is getting worse, or that is causing unusual breathing or problems feeding, call NHS 111 or contact your GP practice.
"As a parent trust your judgement and if your baby seems seriously unwell go to A&E or call 999."
Dr Watson also shared some tips for protecting your baby against winter bugs.
"Washing your hands regularly and using tissues can reduce the spread of RSV and other viruses," he said.
"People who are unwell with colds should try and avoid visiting newborn babies and other vulnerable groups."
UKHSA also shared updates on Covid and flu cases.
Dr Jamie Lopez Bernal, a consultant epidemiologist at UKHSA, said: "This week's data shows that Covid-19 remains at low to moderate levels.
"Flu positivity is gradually increasing, however levels remain low.
"We expect viral respiratory infections to increase as the season progresses, so don't wait for it to hit your household, get vaccinated and make sure you are protected this winter."
It comes after the health watchdog urged the "missing million" - vulnerable Brits who haven't taken up their flu, Covid and RSV shots - to get vaccinated for vital protection against dangerous bugs.
A new Covid-19 variant dubbed XEC that's spreading "rapidly" across the globe has experts on the lookout.
Dr Lopez Bernal said: "Our current surveillance shows that around one in 10 sequenced Covid cases are the 'XEC' lineage however information doesn't suggest we should be more concerned about this variant.
"We are monitoring this closely and vaccination still offers the best protection.
"If you are showing symptoms of flu or Covid-19 such as a high temperature, cough, and feeling tired and achy, try to limit your contact with others, especially those who are vulnerable."