Coronavirus cases are doubling about twice as fast in Yorkshire, the North West and the West Midlands as for the whole of England, according to the largest Covid-19 study of its kind.
Experts behind the study suggested the rate of growth of the epidemic across England has slowed in the last month, but the country was now at a "critical point in the second wave".
It found cases are doubling every 29 days in England, much slower than estimated for the period mid August to early September, resulting in a national reproductive rate (the R number) of 1.16.
However, at a regional level, the team estimated cases are doubling much quicker - every 13 days in Yorkshire and Northern Lincolnshire.
Across England, about one in 170 people currently have the virus and there are approximately 45,000 new infections each day, the report continued.
The study pointed to "high prevalence" of Covid-19 across England and said "prevalence has increased in all age groups, including those at highest risk".
The highest prevalence of the virus is among 18 to 24-year olds, but prevalence among anyone aged 65 and over has increased eight-fold since mid August to early September, to 0.33%, the report said.
It also found that at least half of people with Covid-19 will also not display symptoms on the day of testing or in the previous week.
The report put the R value at 1.37 in Yorkshire and Northern Lincolnshire.
There are claims the data could support further restrictions in the north of England "sooner rather than later".