Across the UK 40 areas have seen rising infection rates over the past week, including five in the West Midlands, while the number of new cases in the Black Country went up 10 per cent over the period to 925.
The rise comes amid warnings that too many people were bending the rules ahead of the relaxation of lockdown measures.
Boris Johnson has warned that soaring cases in Europe were likely to hit the UK.
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In the seven days to March 18, Dudley's rate rose by 50 per cent to 79.3 per 100,000 people after 255 new cases were recorded.
The rate in Wolverhampton went up 24 per cent to 72.1, Cannock Chase's rate was 68.5, up 23 per cent, and in South Staffordshire there was a 15 per cent rise to 61.4 cases per 100,000.
However, the vast majority of those at risk of dying have received the first dose of their vaccine.
Dr Lisa McNally, Sandwell's director of public health, said the return of schools and increased rapid testing may have contributed to a rise in cases.
But she said a third wave could be on the horizon as too many people were "starting to relax" and not sticking to the rules, which was partly due to "lockdown fatigue" and the success of the vaccine programme.
She said: "It is understandable that people are getting tired of lockdown, but we have to finish the job.
"If we drop our guard we will be heading towards another wave of cases, and just how big that is depends entirely on all of us."
Dr McNally said case rates across the region were still higher than they were last July.
She said the Kent variant – which spreads more easily and has a higher fatality rate than other strains – was "easily the most dominant strain" in the region, and that while the vaccination programme had been "a huge success", around half of the population were yet to receive the jab.
"At the moment we are still extremely vulnerable as a population," Dr McNally said.
"This virus is going to take more lives, and everyone has to ask themselves how determined am I to do the best I can to make sure that it's not me or a family member.
"The battle is nowhere near over."
Police and health leaders in Wolverhampton have also called on people to be vigilant to avoid "further heartache" caused by Covid-19.
John Denley, director of public health, and Superintendent Simon Inglis made the plea as lockdown restrictions are slowly eased.
Mr Denley offered his condolences to people who have lost ones as he called the upcoming weeks and months the "most critical" yet.
Superintendent Simon Inglis of Wolverhampton Police, added: "The last year has been like no other. We have faced some significant challenges and will do so again moving forward.
"However, we still have some tough times ahead and we would ask that you continue to support us as we help the city come slowly out of lockdown."
Additional reporting by Thomas Parkes