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."
Get the best features, fun and footballing frolics straight to your inbox every week.
Thank you for signing up to Four Four Two. You will receive a verification email shortly.
There was a problem. Please refresh the page and try again.