The new cases have nearly doubled, with the weekly infection rate increasing from 13.8 per 100,000 people to 28.1.
The rate has not yet met those of the worst affected areas, but officials have urged caution.
Birmingham City council joined with others in the West Midlands and asked businesses to remain vigilant.
The council, in conjunction with Coventry, Sandwell, Solihull, Dudley, Walsall and Wolverhampton, said returning students could add another risk.
