Mr Allan, of Australia, said he was usually a sociable player, but the sickness meant his concentration and attention was limited to the cards he held.
"I played well, partially because I was only concentrating on the cards I had."
By the time he reached "heads up", when only two players remained, he admitted he probably came across as "rude" to his unknowing opponent.
"I wasn't doing anything to the point where I was being rude.
"I was just sitting there with my head in my hands, almost falling asleep"
His win on Sunday night at the Texas Hold'em style tournament was his first in live poker, although he has previously had success in online games.
As fortune would have it, he was "lucky the way it panned out" in terms of seating arrangements, and he made his bets following second-place winner, Ken Demlakian, who in turn had the advantage of knowing what third-place winner, Jordan Westmorland, bet.
Rather than taking the $3000 entry-fee tournament as serious as some, Mr Allan, like many visitors before him, saw Queenstown as a holiday destination.
"It was more of a holiday, but if you win it's a bonus."
"It takes a lot of luck to win a poker tournament."
His winning hand, a 10 and six of spades trumped Mr Demlakian's seven of hearts and three of diamonds for the flush and the title.
"The last card completed the flush for me.
"That's what happens when you play heads up, you get a lot of weak hands playing against other weak hands."
As for the origins of his flu, he sternly believed it was doing the rounds at poker tournaments.
"Everyone caught it, there was a poker tournament in Melbourne a week ago, [another player] got sick and I'm pretty sure I caught it from him.
"But I wouldn't say we did ourselves any favours in terms of our nocturnal activities."
