Birmingham remain just three popints behind Wolves in second place after their away win at Doncaster and Wolves are yet to face the Blues at St Andrews this season.
"It's a relief to win and a big help that Reading are still in their bad run," McCarthy said after the Charlton game.
"Hopefully, it will continue until the end of the season. I'm certainly not getting carried away, though.
"There are still seven games to go and you'll have to wait until May to see if I have a smile on my face."