Coronavirus cases have almost doubled in Great Yarmouth after falling in previous weeks - with two communities bearing the brunt of new infections.
Data from Public Health England shows the borough's rate of infection increased to 119.8 per 100,000 people last week, up from 66.4 the week before.
The biggest increases were in Caister and Gorleston West.
The former had 11 cases in the week ending November 25 - that number had jumped to 23 infections in the seven days leading up to December 2.
In Gorleston West, the increase for the same time period was from 9 to 25 cases.
While the national average for cases per 100,000 currrently stands at 148.8, and has been falling, the rate in both communities has more than doubled.
In Caister the rate climbed from 112.3 to 255.7 and in Gorleston West from 120 to 333.4.
Carl Smith, leader of Great Yarmouth Borough Council, said: "We knew there would be peaks and troughs. We're better off than two or three weeks ago. People have just go to take care, wearing masks indoors.
"The figures will fluctuate but the borough is still below the national average," he added.
Mr Smith said the spike in cases could not be put down to one thing as the virus is "out there in the community".
"So we're saying to people don't mix with other households, because this virus does spread in indoor settings. It is a community spread. If the community works with us hopefully we can keep our numbers down."
Tiers across the country will be reviewed by the government next week - and Mr Smith said the hope is that Norfolk would move to Tier 1.
"We have made the case in favour of Norfolk to be looked at as a region, but the East of England is where we are at the moment.
"But hopefully we can get back to just Norfolk and with our numbers you would like to think we would be judged as a Tier 1," he said.
Penny Carpenter, a borough councillor based in Caister, said: "We must never let our guard down, even though there's a vaccinne, but we've still got to be vigilant and treat all this very seriously.
She said it is "very sad" for people who have been infected, and for their family members.
"It's a terrible thing and it's struck families up and down the country. It's one of the worst things I've ever seen happen to people in many a long year," she added.
Coronavirus cases in Great Yarmouth borough for seven days up to December 2 (week leading up to November 25 in brackets):
Bradwell South and Hopton 8 (7)
Caister 23 (11)
Fleggburgh, Rollesby and Martham 7 (4)
Gorleston North 9 (3)
Gorleston South and Beach 10 (12)
Gorleston West 25 (9)
Hemsby and Ormesby 5 (0)
Southtown and Cobholm 12 (7)
Yarmouth Central and Northgate 7 (4)
Yarmouth North 7 (8)
Yarmouth Parade 5 (4)
Cases per 100,000 up to December 2 (up to November 25 in brackets):
Bradwell South and Hopton 110.6 (96.8) Caister 255.7 (122.3)
Fleggburgh, Rollesby and Martham 92.9 (53.1) Gorleston North 114 (38)
Gorleston South and Beach 113.5 (136.2)
Gorleston West 333.4 (120)
Hemsby and Ormesby 55.1 (0)
Southtown and Cobholm 160.1 (93.4)
Yarmouth Central and Northgate 92.7 (53)
Yarmouth North 118.2 (135)
Yarmouth Parade 51.5 (41.2)
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