The number of children under 15 who have died from strep A in the UK has risen to 15, the UK’s Health Safety Agency has said.
New figures from England show the death toll since September has risen to 13.
The other two fatalities were reported in Wales and Northern Ireland.
Diseases caused by Strep A include scarlet fever, strep throat, and the skin infection impetigo.
Although most infections are mild, the bacteria can develop into a life-threatening disease called invasive group A streptococcal disease.
Since September, the UKHSA said there had been 652 reports of the invasive form of the disease, which is higher than during the same period in the last five years.
In the current season of Strep A infections, there have been 85 cases in children aged one to four.
This compares with 194 infections in this age group during the whole of the last high season in 2017/2018.
There have also been 60 cases in children aged five to nine. Since September, 60 deaths have been reported across all age groups in England.
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2:39 ‘Very worrying’: Penicillin shortage parents
Read more: ‘Close the school and keep it closed until Christmas is over’: Worried parents as cases rise. Find out how many serious infections and cases of scarlet fever there are in your area
The increase in infections is thought to be due to large amounts of bacteria and increased social mixing, the UKHSA added.
There is no current evidence that a new strain is circulating, the agency said.
“There are many winter bugs out there that can make your child feel unwell, most of which are nothing to worry about,” said UKHSA Deputy Director Dr Colin Brown.
“However, make sure you talk to a health professional if your child gets worse after a bout of scarlet fever, a sore throat or a respiratory infection; watch out for signs such as a fever that doesn’t go down, dehydration, extreme tiredness, and difficulty breathing.”
While Health Secretary Steve Barclay has said there is no shortage of drugs, pharmacists have complained about a lack of antibiotics, including the liquid version of penicillin, which is often given to children .
The National Pharmacy Association has pointed to “mistakes” in the supply chain for liquid penicillin, while the Association of Independent Multiple Pharmacies said pharmacists were struggling to get everything they needed.