Wouldn't the modified virus need to have a selective advantage to outcompete the normal oral herpes virus? (And since viruses don't reproduce sexually, you can't use a gene drive.)
Not with a gene drive, that's the whole idea behknd it AFAIK. A gene drive copies itself and the payload to 100% of the host's offspring. So, as long as a host is able to reproduce (which granted has lots of implications) it will spread the payload. This accelerates the spreading of a gene tremendously, covering the whole population in just a few generations.
I was trying to make a point a virus can be "benign" like herpes and silently spread effecting a large population.
You don't need a selective advantage as the virus is not competing for scarce amount of resources. You can have herpes and still spread common cold.
