Good news everyone, it was a false alarm.
Was worried that the WKD was so corrosive it had burned through my stomach into my transverse colon but on further investigation it turns out that WKD lemon smells of farts.
As a further piece of good news, I clearly don't have COVID.
(Agent Pr1ck llǝɯs ǝɥʇ sʇI ˙ǝɔɐld sᴉɥʇ ǝʇɐɥ l, Sat 10 Jul 2021, 20:26, archived)