The Wales international is suffering from severe tonsillitis, and has not featured for United since December 8.
The 20-year-old actually Tweeted from hospital before the trip to Aston Villa, with a picture of himself receiving treatment.
He missed the subsequent 3-0 Boxing Day win over Sunderland, and is ruled out of Saturday’s visit of Bolton Wanderers and the New Year’s Day trip to Derby County.
Asked about Brooks’s fitness, Blades manager Chris Wilder smiled: “I don’t know, I have not checked social media. I can keep this going for a little while.”
But Wilder confirmed: “He’s not in a good way, so we have wrote him off for this little period and see what happens in the New Year.
“He’s at home now and hopefully getting better by the day.”
The Blades have no new injury worries for the Bolton game, while midfielder John Fleck returns after serving a three-match ban.
Wilder said: “Everybody has come through Saturday and Tuesday okay, so that’s good news.”