What causes scarlet fever to infect someone and what are the symptoms?

Strep A + gene. Group a streptococcus is cause of throat infections. It is acquired from contaminated fingers or contact with oral secretions of a source case. Some people carry it without getting infected year round. Some strains have additional genes that code for making a toxin that spreads thru the blood & gives a red, sandpaper & sunburn like rash starting within 12 hrs of the fever.