Isn't everybody forgetting that Herpes is incurable?? It's a virus, forgodssakes. No matter what suppressants you take to keep the outbreaks to a minimum, like Valtrax, it will NEVER leave your body.
The virus remains dormant in your body between outbreks, but there is no way of telling if you will have an outbreak tomorrow on set even if you don't show any signs of sores today. And you can very well be contagious before the sores pop up on your first day of outbreak.
So testing for active sores doesn't really do anything. Here today, gone tomorrow, and vice versa.
And testing for the virus itself, and banning people with herpes from working, would mean the porn industry would lose 99% of the talent. (And I don't care what they tell you, they all have it.)