Actually measles is much more ferocious and dangerous if taken by adults than by children, and the older you get the more risk of complications (also because adults have a much weaker resilience than children).
For this reason, before the vaccine was invented, an attempt was made to have the disease taken as soon as possible, so that they would be immunized forever (now with the vaccine, fortunately, there is no need to do it anymore, avoiding suffering and possible complications for children).
Usually it is a disease with a high rash but not fatal, unless there are complications both in the lungs and encephalitis. It can, however, lead to repercussions for the rest of the patient's life, often and willingly very annoying (I speak from experience, having had measles as a child I was half deaf).