Used to fly with a chap who was a bit of a sex fiend. Once a year he'd take himself off to Vietnam for a fortnight and engage in repeated sex with any woman, in or out of a bordello, that he could get into. He never took precautions. On his return he'd wander in to his local doctor's clinic and have a full blood make up for STDs and AIDs. We of lesser sexual predilections always used to be amazed at the significant trauma he put himself through every year while he waited for the results. This was quite some time ago too, when AIDs was an absolute stigma as well as being in short supply of treatments.
Syphilis can take years to get to the tertiary stage and by then the brain has effectively rotted and treatment, let alone a transplant, is difficult. STD has yet to be described as Silently Terminal Droop but the jingle will be along shortly.