Aguero was subsequently ruled out of the FA Cup match at the Etihad Staidum but has tested negative for the virus.
The Argentina star, who had been in line to make his first start since October due to struggles with injuries, could now also miss Wednesday’s game against Brighton.
Sergio Aguero missed the game against Birmingham as he is self-isolating after coming into contact with someone who tested positive for coronavirus
Pep Guardiola confirmed why Aguero was absence after the victory, saying: ‘He is isolating, unfortunately. He was in contact with one person who was positive.
‘It is a pity. It was a perfect day to get minutes but unfortunately he has to be a few days out.’
City ran out 3-0 winners against Birmingham, with Bernardo Silva scoring a brace, while Phil Foden was also on target.
Pep Guardiola described the situation as ‘a pity’ with Aguero missing out on City’s victory
Kyle Walker, who previously tested positive for Covid-19, returned to action in the win
City welcomed back Kyle Walker and Gabriel Jesus in the win, with both players having previously tested positive for Covid-19.
The game between City and Everton on New Year’s Day had to called off following an outbreak of coronavirus among City players and staff.
Eric Garcia also tested positive as did Ferran Torres, Tommy Doyle, Scott Carson, Cole Palmer and members of City staff.