Possible silly question about Werewolves

[Darklady]

No: HPFGUIDX 78242

I'm sorry if this has been covered , but I searched the posts and 
couldn't find it.

I was listening to my Harry Potter tapes ( unabridged American 
version ) at work today and was suprised by one line. 

(Spoiler here - but not for anything recent ) 

Lupin, in discussing his lycanthropy, says that "they didn't have a 
cure BACK THEN." (Emphasis obviously my own. ) Would that 
not imply that there is a cure NOW? If so - why has not Lupin 
been cured? Is it perhaps like a rabies cure - that is only effective 
if started before the disease takes hold? When was the cure 
discovered? Obviously fairly recently. ( At least within Lupin's 
lifetime.)  Would this explain why the Wolfsbane Potion is 
currently rare? (Because few new werewolves are created - so 
few would need it. ) What effect would this have on current 
werewolves? On the laws re: werewolf bites? ( Which - while still 
dire - would be less terrible if they did not also pass on the 
curse.)

Is this something strange re the Potterverse - or an I 
misunderstanding? Every fan-fic seems to treat lycanthropy as 
an ongoing risk, but? Just curious.

Thank you.