Is soul vortex saving me from disease?

[Immaculate]

I have a unit, a tough little piece of cavalry which continually uses soul vortex in battle but has also picked up the diseased affliction. The thing is, as long as he is involved in combat, his hit points sort of vary up and down and he doesn't die.

Am i imagining things or is he keeping the sucked out life from combat and preventing the disease from killing him thereby?

I.