CHICAGO — The toughest part of having COVID-19 for Jayson Tatum wasn't the headache, the high temperature and chills he experienced. Those symptoms went away after the first night.

Most difficult was the mental toll.

"It was tough, especially your initial reaction once you find out," he said. "I don't know if it's panic. But you definitely worry because of everything you read about it and hear, how many people it's affected and how many people didn't make it."

Tatum scored 24 points after missing five games, Jaylen Brown had 26 and the Boston Celtics beat the Chicago Bulls 119-103 on Monday night.

"The first four days or so, for lack of a better word, it bothered me," Tatum said. "It was on my mind. I was thinking, do I feel OK, do I not feel OK? Can I smell this? Does my chest hurt? Or am I just overthinking?"

Tatum said he felt a bit tired in the first half. But he got a second wind. 

He made three 3-pointers and had five assists over 31 minutes in his first appearance since Jan. 8.

Brown had another solid game following his 33-point outing in Sunday's romp over Cleveland.

Daniel Theis scored 19 points and Marcus Smart added 13 while tying a career high with 11 assists as the Celtics won their second straight.

Zach LaVine led Chicago with 30 points and shot 6 of 10 on 3s. But he also committed six turnovers, giving him 13 in the past two games.

Lauri Markkanen scored 18. Thaddeus Young just missed a triple-double with 16 points, nine rebounds and nine assists, but the Bulls dropped their second in a row after three consecutive wins.

"They're all going to need to learn how to win," coach Billy Donovan said. "I wish I could snap my finger or pour something on it to make it just happen. But it doesn't work that way. Unfortunately, before you win, there's generally a lot of suffering."

TAKING CONTROL

Smart scored 13 and Brown and Tatum added 11 points each as the Celtics grabbed a 60-50 halftime lead.

Theis' alley-oop dunk and layup in the final 30 seconds sent Boston to the locker room up by 10 and set off an 18-2 run.

Brown scored seven as the Celtics reeled off the first 11 points in the third quarter. Tatum answered a hook shot by Young with a 3-pointer to make it 74-52, and the Celtics withstood a few pushes by Chicago to come away with the win.

TIP-INS

Celtics: G Kemba Walker was held out. The four-time All-Star played the previous four games after missing the first 11 because of a left knee injury. … Boston was 15 of 29 on 3s, with Aaron Nesmith hitting three and finishing with nine points. … Theis also had three steals and three blocks. … Tristan Thompson grabbed 10 rebounds. … Coach Brad Stevens said Tatum wasn't on a specific minutes restriction, though the Celtics weren't going to let him reach the high 30s.

Bulls: C Wendell Carter Jr. (bruised right quadriceps) will be evaluated toward the end of the week after he missed his third consecutive game. Donovan said Carter is improving, though he hasn't been participating in any on-court activities. The Bulls are off until the Portland Trail Blazers visit on Saturday. Their game at Memphis on Wednesday got called off because of the Grizzlies' COVID-19 issues. … Otto Porter Jr. scored 13 points and hit four 3s. … The Bulls were 4 of 10 from the foul line.

UP NEXT

Celtics: Were scheduled to visit DeMar DeRozan and the San Antonio Spurs on Wednesday. Whether the Celtics actually make that trip was up in the air after Monday's game between the Spurs and Pelicans was postponed because the NBA determined neither team would have enough players available. "My thought would be we should not fly there until we know. That's the bottom line. That's my only thought going through my mind with all the travel we have coming up," Stevens said.

Bulls: Chicago hosts Damian Lillard and the Trail Blazers on Saturday.