Board Thread:Skyrim/@comment-11204276-20130822224324/@comment-6881629-20150526145711

Go to a vampire den (when your already a werewolf) turn the difficulty down and stand there letting them attack and cast drain on you until you catch the diseases you could try some light punches to take their health down a bit but but don't kill them so they keep attacking giving you more chances to catch it.

There is only a small chance to catch it with the werewolves disease resistance it could take ages (or it could not).