Health officials are urging parents to look out for symptoms of Strep A after six children died with an invasive form of the bacterial infection.
Strep A infections are usually mild, causing illness ranging from a sore throat to scarlet fever, but can develop into a more serious invasive Group A Strep (iGAS) infection.
The rise in Strep A cases and deaths is most likely due to high amounts of the bacteria circulating and increased social mixing, the UKHSA said.
Speaking to BBC Radio 4's Today programme on Saturday, infectious diseases paediatrician Prof Kampmann said Strep A caused "an asymptomatic infection in the majority of people, then there is a sore throat, then scarlet fever, and in a very, very small minority will there be invasive Group A Strep".
She said there had been three times as much scarlet fever this year than was seen pre-pandemic: "It starts off with a high fever, very sore throat and very red tongue, which has this sort of papillae - eventually developing a rash which feels a bit like sandpaper.
Prof Kampmann said if children became really unwell, or if parents were in doubt, they should seek help.
The latest data shows there were 851 cases of scarlet fever reported in the week of 14-20 November, compared to an average of 186 for the preceding years.
Virologist Dr Chris Smith said the general rise in Strep A infections could be due to a drop in immunity following the pandemic.
There have been 2.3 cases of the invasive Strep A disease per 100,000 children aged one to four in England this year, compared with an average of 0.5 in pre-pandemic seasons of 2017-19, the UKHSA said.