Scarlet fever and scarletina are the same thing, more commonly called scarletina these days. It is a bacterial childhood illness that is characterised by very high temperature, a fine red rash, sore throat and what they call a rasberry tongue as you get spots on your tongue that look like .... you got it!!! a raspberry.
Before antibiotics came in after the war it was quite a serious thing as small kids and frail kids eg those with TB, could die of it so they were very frightened by it. These days you just go to the GP when your kid's unwell and get antibiotics so I expect they catch quite a bit before it gets too bad.
Aren't we lucky they discovered penicillin.