The spread of the Indian Covid variant in the UK is causing concern for ministers and health officials.
Prime Minister Boris Johnson admitted he is “anxious” about the new strain, known as B.1.617.2, as new figures show case numbers of the variant are rising.
It is proving to be highly transmissible and is thought to be one of the main reasons there has been a spike in cases in Bolton Greater Manchester.
The town now has the worst infection rate in the UK.
So, what is happening in Bolton - and will there be a local lockdown?
Here is everything you need to know.
Why has there been a surge of Covid cases in Bolton?
Bolton has seen a sharp surge in infections since mid-April.
Rates doubled in the last week of that month, then doubled again during the first week of May.
The spike means that Bolton areas now account for six out of the 10 regions in the UK with the highest infection rates.
Samples from the town were sent to Public Health England which identified the B.1.617.2 Covid variant first spotted in India earlier in 2021.
B.1.617.2 now accounts for the majority of new coronavirus cases in Bolton.
It is thought that initial cases of the variant in the area were linked to international travel, but there is now widespread community transmission.
What else is causing the spike?
Official data shows that the infection rate has been driven by a large surge in cases among schoolchildren.
PHE figures revealed that the number of positive tests among children under 14 years old had tripled in a week.
But while the highest rates are in the younger age groups, increases are happening across all the under 60s.
Health officials say this could suggest transmission within households.
Younger adults may have been exposed to the virus through their school-age children, or picked it up at their workplace.
Fortunately, there has so far been no increase in infections among those over 60 years old, with officials hoping that the vaccine rollout will protect this more vulnerable demographic.
What measures are being rolled out?
The government is looking for a solution to combat the rising cases in Bolton.
So far, the local council has set up mobile testing units and door-to-door visits have been made to hand out self-testing kits.
Enhanced contact tracing has also been put in place, with those who have been close to a positive case getting tested instead of just told to self-isolate.
And the NHS is now sending out a mobile vaccine bus into the parts of the town with the highest infections.
It is thought that door-to-door jabs are also being considered.
But England is only days away from another national relaxation of Covid rules on 17 May, when people will be allowed to mix in homes again and indoor hospitality will reopen.
Could there be a local lockdown in Bolton?
There are fears that local lockdown measures could be imposed in hotspot areas such as Bolton.
Mr Johnson has warned that the planned easing could be pushed back if the Indian variant “takes off”.
Admitting he was “anxious” about the new strain, the Prime Minister said there may be “things we have to do locally” including surge testing and tracing.
However, he did not rule out a return to a local lockdown system - but such a move is likely to be resisted in Bolton.
The mayor of Greater Manchester, Andy Burnham, has instead been calling for a “surge vaccination” strategy, which ministers are understood to be considering for areas with high case rates.
This would mean that jabs would be made available to younger age groups instead of making them wait their turn.
And councillor David Greenhalgh, leader of Bolton Council, has called on the government not to lock the town down again and instead focus on vaccinations for over-18s.
He told the Manchester Evening News: "We have been here before. All that will happen is people will travel outside the borough, sometimes 50 yards up the road across a boundary to access hospitality. It does not work. And our hospitality is left struggling again, and on its knees.
“More targeted vaccines please and allow us to re-open.”