Manchester City have confirmed that defender Kyle Walker, striker Gabriel Jesus and two staff members have tested positive for the coronavirus.
Both players featured in City's 4-1 League Cup quarter-final win over Arsenal on Tuesday.
"Manchester City FC can confirm that Gabriel Jesus, Kyle Walker, and two members of staff have tested positive for COVID-19.
"All four 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 our colleagues a speedy recovery over the Christmas period ahead of their return to work, training and competition."
Under Premier League regulations, players or club staff who have tested positive will self-isolate for a period of 10 days.
That is likely to rule Jesus and Walker out of trips to Everton and Chelsea, as well as their Boxing Day home clash against Newcastle.
Walker and Jesus could be available for their League Cup semi-final against Manchester United on January 6.