Harry and Liam both got weed on by a koala when the band stopped off at a sanctuary in Brisbane for a photo op with the cuddly creatures.
Eighty per cent of koalas carry chlamydia, so the lads have been warned that there's a chance they may have picked something up "down under".
"I'm genuinely scared," The Sun quoted 18-year-old Liam as saying. "This is worrying. I’d have never picked the thing up if I’d known."
But Harry isn't letting the risk of a marsupial-borne STD get in the way of his love life.
The Casanova of the band broke a million little girls' hearts when he was snapped pashing US model Emma Ostilly on a date in Auckland at the weekend.
An onlooker told the Daily Mirror, "They really seemed to have a connection and only had eyes for each other … They were enjoying themselves, laughing and joking together."
Meanwhile, Liam and Louis Tomlinson were the two band members brave enough to have a go at bungee jumping off Auckland's Sky Tower yesterday.
Harry, Niall and Zayn didn't join in, but check out this hilarious video of Zayn trying to pronounce "bungee jumping"!