Van Dijk has been linked with a mid-season move away from Celtic Park, with Premier League sides Arsenal and Sunderland among those rumoured to be interested in the Dutchman.
But Deila insists that the 23-year-old centre-back is content with life at the Scottish Premiership champions.
"He's [Van Dijk] very happy," Deila said. "I have spoken with him and we are very happy to keep him as well. He's a top player.
"For me, Virgil's developing now and taking steps all the time which is very important. I am so happy to have him.
"He is enjoying his football, playing well. That's positive. He is such an important player for us.
"He's worth a lot of money but I am very calm. In my opinion he is a very good player now but he can be a world-class player.
"The next thing for him, even though he's just 23, is to become a leader in defence who controls things. He's starting to do that but there are still a lot things to work on."
