Oh no, herpes simplex mutated inside a man in France at a kissing festival-the mutation causes HIV like symptoms (AIDS) 20 years after infection. Yet no one seems to notice since you simply have AIDS symptoms and are speculated to have contracted HIV.
Would it rapidly spread just like regular cold sore herpes infected a big portion of humans?
Could it wipe out humanity?
How would society/the governments react after the first victims?
Edit: AIDS and HIV are just widely known examples for fatal uncureable diseases. Not to be taken literally- the idea is certain premature death