The rate of Covid-19 cases in Norwich has more than doubled in the space of a week.
Between 4 and 10 October the incidence in the city was 92 cases per 100,000 people - up from 36 a week before.
Norfolk's director of public health Dr Louise Smith said she was "concerned there is a trend of rising cases in the Norwich area".
Covid-19 support officers would aim to stem the rise by checking on social distancing, the city council said.
The figure is still well below some of the worst-affected areas in the UK, such as Knowsley on Merseyside, which had 701 cases per 100,000 between 6 and 12 October.
"The rate of infection is still below the national average and we want to keep it that way," said Dr Smith.
"At the moment we are seeing the number of cases grow each day, particularly among young adults, and we know that the virus can spread quickly from young people to the wider community and to those who are more vulnerable."
Where are the current hotspots?
There are several local hotspots in the UK where cases have spiked in recent weeks.
The orange areas on the map below are those currently seeing the highest number of cases per 100,000 people.
Sorry, your browser cannot display this map
Dr Smith said that on average 20 cases were being diagnosed a day - and that most new cases were people aged 18 to 30.
Alan Waters, leader of Norwich City Council, said the council had been given an £88,000 grant to employ support officers to help ensure Covid-19 social distancing rules were followed.
He said now that "Norwich has the highest rate of positive Covid cases in Norfolk per 100,000 people.
"We need to act now to drive the numbers down so I'm urging all our residents, throughout our many different communities and neighbourhoods, to act as one and follow the government guidance so we can protect ourselves, protect others and protect Norwich".