I don't think they used to be *that* virulent. In 2nd Ed, you had a 2% chance per point of damage suffered to contract lycanthropy. Given some of the creature, like werewolves, only might have been doing 1-6 damage or something like that, per attack, that means on average *if* you got hit (which wasn't often, given they had predefined Thac0's), you had like a 6% average chance per hit to get infected.
I houseruled that the chance was cumulative during each combat, for all damage by a single lycanthrope. So if got hit 3 times, for 3 damage each, you rolled once at the end of the combat, and would have a 18% chance to contract.
I think in 3E it's *easier* for low level victims to be infected, because they could be hit for even a low amount of damage, and whether they get hit for 1 point, or 10 points, they've got an equal chance to be infected...which is more in line with mythology.
I think the only change to the virulence factor is that infected lycanthropes can't infect others.
Banshee