Renato Sanches, Jonathan Bamba and Jonathan Ikone were all absent as Christophe Galtier’s men defeated Mouscron 2-1 in a friendly game on Saturday.
The Lille manager revealed afterwards that the trio were absent because they had tested positive for the virus during a recent eight-day break afforded to the players.
"Renato is in Portugal. He must undergo two negative tests to be allowed to travel," said Galtier.
"As for the two Jonathans, they are in France and will soon be back with the team, probably this Monday.
"After the first phase of training there were eight days of rest, and during those eight days the players contracted the virus.
"The players are fine, but we are waiting to see the results of the next tests."
Sanches, who won EURO 2016 with Portugal, joined Lille from Bayern Munich last year.
Lille finished fourth in the Ligue 1 last season after the coronavirus pandemic led to an early conclusion of the campaign and they will play in the Europa League next season.
They will host Rennes in the opening game of the season when the Ligue 1 returns for the 2020/2021 season on August 22.
