Backstreet Boys share their secret to longevity

LAS VEGAS, NV - MARCH 01:  (L-R) Brian Littrell, Kevin Richardson, Nick Carter, AJ McLean and Howie Dorough of the Backstreet Boys perform during the launch of the group's residency "Larger Than Life" at The Axis at Planet Hollywood Resort & Casino on March 1, 2017 in Las Vegas, Nevada.

(CNN)In the absence of dancing bodies and screaming fans, the theater inside Planet Hollywood Casino and Resort is shiver-inducingly cold and cavernous. The sniffles emitting from A.J. McLean and Kevin Richardson echo a bit as a result.

They're fighting sinus infections. In fact, all of the Backstreet Boys are, Richardson said.
"I just had sinus surgery," McLean shared. "Now that I can breathe, it's awesome. But now I'm getting everything."
The nearly 5,000 fans that were in attendance a little less than 18 hours prior certainly didn't seem to notice.
    The energy was, you could say, larger than life on opening night of the Backstreet Boys's residency at The Axis, a space that also hosts Britney Spears's Pieces of Me show and Jennifer Lopez's All I Have. (Lopez's show vacated days before BSB's March 2 opening, leaving them with just a couple of days to practice on their new stage.)
    Organizers call it one of the fastest-selling shows in Las Vegas history. It als