Major question on an Infected evolution into an immune type

Okay this just popped into my head and i might use this pokemon as a charactor but here's my question.

Let's take this Cascoon for example,
It's a pure bug type and this cascoon i'm using for this example is Infected.

So now we have an Infected Cascoon here, so everything is all fine and dandy with the Rules but then it Evolves into Dustox, a BUG/POISON DUEL TYPE!

Okay so now comes the mind bending part, The Infected Cascoon is now an Immune Dustox!

So is it now cured as in not infected, or is it still infected? I don't really know because Poison types are immune to the epidemic, but the now Dustox was an infected cascoon so would it not be able to evolve and be stuck as a infected cascoon For all of enternity?

Okay you can now say if it's still infeected or not ;)

P.S. Sorry if this question just broke your minds, it kinda broke mine :b

Only pure Poison-types count, Shadowhope :3 As said in an earlier question answered by the admins, any other type "dilutes" the Poison-type Pokemon's ability to resist infection and renders them vulnerable.

Dustox, being a Bug/Poison type, is thus able to suffer from the Epidemic Virus. Only pure Poison-types such as Swalot, Seviper, Muk, and Nidorino are immune to the virus, out of all of the Pokemon in the series.

Only pure poison types are immune, I believe. [That or primary poison types.]

A dual type with poison would still be infected. :>

EDIT: Lol Veil beat me to it. xD

Okay thanks.