Eldrain retorts, "that's preposterous! While disease can turn a man's stomach inside out or make his flesh burst into boils, the sanctity of one's bloodline can only be disturbed by the most powerful of curses. If you aren't making this up it's probably some trick played by some orc trying to infiltrate proper society."
You grin. "Oh for most of us, sure. This illness here just gives you the itchy ears, a scratch in the throat, maybe leaves you a bit tired..." You give your ear a good scratch. "But if you're an elf? Seems like there's something about it that turns the usual immunities back on themselves or something. Weirdest thing." You make your way over to Eldrain as you say this, just in time to cough in his face. "Glad you're not worried though, I think I might have picked a case of it up myself. Going to take it easy for the rest of the day I think."
You head back to your chambers and ponder just how humiliating to make this whole ordeal for him. Maybe you'll have him begging for a remedy made from absurd ingredients, maybe you really will turn him into some wanton savage orc wench. Perhaps one who can't even speak in complete sentences, or control her urges...
You spend the rest of the day using your new powers to modify your chambers, setting up a personal scrying orb to keep an eye on things... and search for saucy savage she-orcs in the wild for... inspiration.
Worried you might forget, just before bed you use the chronivac to set a few small changes into motion. First, after a day, his ears are to start itching uncontrollably, a tingle in the throat by morning, strange cravings for mushrooms and cave roots that afternoon... and then the real fun as he starts to turn a sickly shade of green by evening...