'Dancing With the Stars': Maksim Chmerkovskiy in for Derek Hough

Like the celebrities, the "Dancing With the Stars" pros aren't immune to being sidelined for their health.

Derek Hough has fallen ill from flu-like symptoms, and will be replaced by ousted pro Maksim Chmerkovskiy to partner Joanna Krupa Monday night.

"My whole body is aching like crazy. I can barely stand up.... And I'm coughing like crazy," Hough had tweeted Thursday, later adding, "At the docs for 3 hrs today ... Had a temprature [sic] of 104 ... Had an IV in my arm for 2hrs ... Maks is steppin up for me helpin jo."

At first it seemed that Chmerkovskiy -- who was eliminated with celeb partner Debi Mazar -- would only step in for rehearsals, but it appears that he'll now partner with Krupa for all three routines of the night.  It's not clear if Hough will be well enough after that to resume his work.

Chmerkovskiy will have to keep his focus on the competition and not on ex-fiancee Karina Smirnoff and her celeb partner Aaron Carter.

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