Health experts are investigating cases of Strep A infection after six deaths of young children and a rise in cases.
The UK Health Security Agency (UKHSA) said there had been a rise in cases of rare invasive Group A strep this year, particularly in children under 10 years old, with five deaths this season in England.
A pupil from Victoria primary school in Penarth, Wales, four miles south of Cardiff, has also died.
Group A strep bacteria can cause many different infections, ranging from minor illnesses to deadly diseases.
They include the skin infection impetigo, scarlet fever and strep throat.
While the vast majority of infections are relatively mild, sometimes the bacteria cause a life-threatening illness called invasive Group A Streptococcal disease.
UKHSA said there is no evidence that a new strain is circulating, currently and the increase is most likely related to high amounts of circulating bacteria and social mixing.
During the last high season for Group A Strep infection (2017 to 2018) there were four deaths in children under 10 years old during the equivalent period.
Dr Colin Brown, deputy director said UKHSA, said: “We are seeing a higher number of cases of Group A strep this year than usual.
“The bacteria usually causes a mild infection producing sore throats or scarlet fever that can be easily treated with antibiotics. In very rare circumstances, this bacteria can get into the bloodstream and cause serious illness – called invasive Group A strep (iGAS).
“This is still uncommon; however, it is important that parents are on the lookout for symptoms and see a doctor as quickly as possible so that their child can be treated and we can stop the infection becoming serious.
“Make sure you talk to a health professional if your child is showing signs of deteriorating after a bout of scarlet fever, a sore throat, or a respiratory infection.”