This valuable UK study gathers national data on the number of scarlet fever notifications each year from 1911 to 2016, and explores the characteristics around the rather dramatic increase since 2014.

It's useful to note that scarlet fever, like many infectious diseases, moves in cycles, with peaks and troughs. What it can't easily tell us is the reason why there should have been such a massive surge in cases since 2014, which does not seem to follow the natural cycle.