Xherdan Shaqiri has become the third Liverpool player to test positive for coronavirus in the last seven days.
Players jetted off on Monday to join up with their national teams as domestic football takes a break for the next 10 days.
The Switzerland FA confirmed on Tuesday morning that Shaqiri had tested positive for Covid-19.
A statement read: "Xherdan Shaqiri has tested positive for Covid-19. In consultation with the health authorities, he is in isolation.
"The strict protective measures and requirements of UEFA for national teams in accordance with the 'UEFA Return to Play Protocol' have been strictly adhered to since the move began.
"Based on this, clarifications are currently underway with the local health authorities about how to proceed."
Shaqiri will now be forced to withdraw from international duty with Switzerland as his country get set to play Croatia in a friendly tomorrow night before two Nations League matches against Spain and Germany.
However, in line with self-isolation guidelines Shaqiri could be out of quarantine within 10 days and therefore available for the Merseyside derby at Everton on Saturday, October 17, should his health and fitness allow.
Last week, Thiago Alcantara became the first Liverpool player to go public after contracting the virus.
Sadio Mane then followed suit on Friday, having missed training at Melwood after also testing positive.
Both players have also already started a 10-day period of isolation but should be free to face the Blues upon the resumption of the domestic campaign.
