gov.uk/government/news/ukhs...
Extract:
"Scarlet fever is caused by bacteria called group A streptococci. These bacteria also cause other respiratory and skin infections such as strep throat and impetigo.
In very rare occasions, the bacteria can get into the bloodstream and cause an illness called invasive Group A strep (iGAS). While still uncommon, there has been an increase in invasive Group A strep cases this year, particularly in children under 10".
According to
nhs.uk/conditions/scarlet-f...
scarlet fever is highly contagious, is more prevalent among children than among adults, and the host can be infectious up to six days before symptoms appear.
If you have a weakened immune system you really don't want to risk an invasive strep infection pubmed.ncbi.nlm.nih.gov/282...