Following a 3-2 victory over the Mets, manager Gabe Kapler revealed that Solano felt cold-like symptoms earlier in the day. He was placed on the COVID-19 injured list just before the game and sent back to the team hotel in New York, where he must quarantine.
The major-league-leading Giants continue their road trip Friday night in Atlanta.
Kapler said the club had completed contact tracing and only hitting coach Justin Viele will be away from the team as a result of Solano's positive test. Viele has since tested negative, Kapler said.
"It's kind of a reality that we're dealing with right now," pitcher Alex Wood said. "We've been fortunate enough to make it this far without having any episodes."
San Francisco has Tommy La Stella to fill in at second base, and the team recalled infielder Thairo Estrada from Triple-A Sacramento. The Giants are trying to hold off the rival Dodgers for first place in the NL West.
Solano is hitting .275 with six homers, 30 RBIs and a .727 OPS. He's made 73 starts out of the team's 127 games, all at second base.
Solano was the Silver Slugger award winner for National League second basemen last year, when he batted .326 with an .828 OPS in 54 games during the pandemic-shortened season.
In addition, All-Star catcher Buster Posey missed his second consecutive game because of discomfort in his left knee.
"No long-term concerns for Buster. Just giving him an additional day. It's what we thought was best," Kapler said before the game.
Posey was on the bench and available in an emergency, according to Kapler.
The 2012 NL MVP has tested the knee in a catcher's squat and felt improvement since being removed Tuesday, his manager said.
"I don't think that he's in a whole lot of pain, it's more about all of the different positions that he can get into in a game and not wanting to come out of a game," Kapler explained.
In other roster moves, first baseman Brandon Belt was placed on the bereavement list to attend his grandmother's funeral Friday in Texas, and San Francisco recalled catcher Chadwick Tromp from Sacramento.
Posey, 34, was pulled in the fifth inning Tuesday night during an 8-0 victory over the Mets after plate umpire Greg Gibson told Kapler that Posey seemed off.
The seven-time All-Star sat out Wednesday's 3-2 win in favor of Curt Casali, who caught most of the series finale as well. Casali was lifted for a pinch-runner (Tromp) in the eighth as a precaution after taking a foul ball off his mask during the game and feeling dizziness at third base.
"He was a little bit shaken up," Kapler said.
Posey is having a resurgent year after skipping the 2020 coronavirus-shortened season when he and his wife adopted twin girls that were born prematurely. He is batting .314 with 15 homers, 39 RBI and a .925 OPS.
Belt hit two home runs Tuesday night and dedicated them to his grandmother after she died that morning. With the funeral service scheduled for Friday, Kapler said Belt was likely to rejoin the team Saturday in Atlanta and be activated Sunday.
"That's not set in stone, but that's where we are right now," Kapler said late Thursday afternoon.
Wilmer Flores played first base for the Giants against his original team.
In addition, right-hander Anthony DeSclafani was scheduled to throw a bullpen with an eye toward coming off the injured list Sunday to start in Atlanta.
DeSclafani exited his Aug. 18 outing against the Mets after getting hurt while covering first base. He was placed on the 10-day IL with right ankle inflammation.