Other than the disease that compels people to wear pants like this, we know of no chronic illnesses affecting the Bieb.
But there doesn't need to be a disease here. Celebrities drop like flies when they're on tour.
If a star has been on tour, it's very likely they've had some kind of onstage stumble, if not a full-scale collapse. Here's the proof:
It's not 100 percent clear what affected Bieber when he collapsed at the O2 Arena in London. We know that he passed out after experiencing shortness of breath; doctors treated him with oxygen before he finished the show and headed to the hospital.
He's since made a return to the arena for his next show.
But given the clues we have, it's safe to assume that Bieber had some combination of dehydration, low blood pressure, low blood sugar, a cold or the dreaded flu.
"I can tell you that the common thread in younger, healthy-appearing people is that they are not getting enough sleep," celebrity internist Dr. Damon Raskin explains to me. "And probably with all the dancing, they're getting dehydrated and maybe not eating well enough.
"They're eating quickly on the road. And if they get low blood sugar or low blood pressure, they can have these episodes of passing out or fainting. He needs to be drinking at least an 8-ounce glass of water every 2 or 3 hours."
Raskin also gently reminds us that "this is also a bad year for respiratory infections and flu."
Whatever is going on inside the Bieb, know this: He is not alone.
Lady Gaga almost collapsed onstage during a New Zealand concert in 2010. She'd previous cited bouts with "exhaustion."
Rihanna did the same thing in 2008 while performing "Umbrella" in Sydney.
Smashing Pumpkins singer Billy Corgan experienced "blacking out and wiping out," in his words, in 2010.
Meat Loaf, Marilyn Manson, Marie Osmond, Steven Tyler—even Bill Nye the Science Guy, really!—all have gone down while performing.
Maybe we need to be sending them cases of Gatorade?