The "disease" here is sentimentality for human. Could be why he wasnt too eager on taking back the captured part of his body, knowing full well that the Institute is making human-IPO hybrid with the cell sample. Sort of a Prometheus figure here, so to speak. Also, the snake guided Eva to the Fruit of Knowledge in the Garden of Eden. Lots of symbolism here
I think the previous chapter has a translation error.
In this version part of the vampire essence's passive was "Hp exponentially increase" but another translation said "increased health regeneration". Considering how he is fighting during this chapter i think the 2' is the correct passive.