Who`s the demon helminth reffers to?

[Loza03]

1 hour ago, Elenortirie said:

I do not recall any mention of tenno (operators) being immune to infestation, (tho considering how they are immune to death, then maybe?) warframes are "immune" because they are already infested - just using a very stable strain that seems to not be randomly spreading to others (helminth to be precise).

The Operator says "We're immune to this infestation". Which granted is fairly vague since it could still just mean 'Whilst we're in the Warframes', but it would match up with the fact it's safe to jump out and run around in Operator form during Infested missions.