Former England goalkeeper Scott Carson, teenager Cole Palmer and a member of staff have all tested positive for coronavirus.
A statement read: ‘ Manchester City FC can confirm that Scott Carson, Cole Palmer and one member of staff have tested positive for COVID-19.
‘Both personnel will now observe a period of self-isolation in accordance with Premier League and UK Government protocol on quarantine.
‘Everyone at the Club wishes Scott, Cole and all of our other colleagues a speedy recovery ahead of their return to work, training and competition.’
Six Manchester City players missed their match with Chelsea on Sunday because of a coronavirus outbreak at the club, while the Premier League was forced to postpone their league clash with Everton just days earlier.
Gabriel Jesus and Kyle Walker were the first confirmed to have had tested positive on Christmas Day.
Four may players as well as three members of backroom staff and a player from the elite development squad also tested positive, which led to the Everton game being called off on December 28.
Ederson, Ferran Torres, Tommy Doyle and Eric Garcia were all left out of the 3-1 win over Chelsea after positive tests and there are further absentees for the crunch semi-final with United.
Ahead of the tie, Guardiola admitted he didn’t have ‘many players’ to choose from.
‘To play one, two games is okay but if sustained for a long time – and you can use just 14 or 15 players – it will be more difficult.
‘But like everyone in the world, we have to adjust in our lives and our profession as much as possible. We don’t have an alternative.
‘The important thing is the guys who have Covid recover well and the others try to avoid it as much as possible.’