The 41-year-old star, freshly back from last week's trip to Ethiopia (where he reportedly assisted Angelina Jolie in picking up a 2-year-old girl she was adopting), checked himself in on Monday night, according to Pitt publicist Cindy Guagenti, who adds that the hospital name is being kept under wraps for security reasons.
She said she was not aware if Pitt might have contracted the illness while in Africa.
Guagenti told the New York Post that doctors performed normal "diagnostic tests" on the actor.
"They just want to make sure it wasn't anything else," she added. "He's doing okay. It's not that big of a deal."