The R number may have fallen below one in some parts of the UK - including the North West, according to new data.
Scientists have said since the beginning of the pandemic that driving the R number below one is the key to suppressing the virus.
The R number represents the average number of people someone with Covid-19 goes on to infect.
When the figure is above one, an outbreak can grow exponentially - but if it is below one, the outbreak will shrink.
Data from the Zoe app coronavirus study run by King’s College London suggests the R number for the whole of the UK is currently around one.
In England, the app says the North West and North East and Yorkshire areas both have R values of 0.9 as cases decline.
But it said “worryingly the East of England and especially the Midlands are both seeing numbers still increasing with R values of 1.1 and one respectively.”
In the South East, London and South West cases are not declining, the researchers said, and the R is one.
The Zoe app team puts the R for the whole of England at 1.0, and at 0.9 in Wales and Scotland.
The latest estimates from the government's Scientific Advisory Group for Emergencies (Sage) put the R number for the UK at between one and 1.2.
Updated estimates are expected to be published by the government at some point today.
It comes as a leading scientists claimed that coronavirus case rates in England are levelling out and may be starting to drop.
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Professor Neil Ferguson, of Imperial College London, told the Guardian infection rates appear to be “plateauing” and may be starting to go down slowly.
But he warned social restrictions may need to remain in large parts of England when the national lockdown ends on December 2 to stop levels rebounding immediately.
