Liverpool midfielder Thiago Alcantara has tested positive for coronavirus, the Premier League club announced on Tuesday.
Thiago missed Monday's 3-1 win over Arsenal and, according to Liverpool, has shown minor symptoms.
The club added that the Spain international is "in good health" and that his condition is improving.
First-team doctor Jim Moxon said: "It is the choice of each individual whether they reveal publicly the outcome of a COVID-19 test.
"We have followed all the protocols to the letter and Thiago is OK. He will be self-isolating now as per the guidelines and hopefully he'll be back with us soon."
Thiago Alcantara has tested positive for COVID-19 and is currently self-isolating according to the necessary guidelines.
— Liverpool FC (@LFC) September 29, 2020
The club has, and will continue to follow, all protocols relating to COVID-19 and Thiago will remain in self-isolation for the required period of time.
Liverpool completed the signing of Thiago from Bayern on September 18, the former Barcelona man taking on a new challenge in the Premier League having won the treble with Hansi Flick's German giants last season.
He enjoyed a stellar debut in Liverpool's 2-0 win against Chelsea at Stamford Bridge after coming on as a half-time substitute.
Thiago had 75 successful passes, the most by any player to have played a maximum of 45 minutes in a Premier League match since Opta began collecting passing data in 2003.
He is set to miss Liverpool's EFL Cup tie with Arsenal on Thursday and the Premier League clash with Aston Villa on Sunday, the last game for Jurgen Klopp's side before the international break.
His positive test also appears to put Thiago's selection in the squad for Spain's friendly with Portugal and UEFA Nations League games with Switzerland and Ukraine in doubt.
Liverpool will resume their season after that break with a Merseyside derby trip to Everton on October 17.