On Monday evening the government announced restrictions on daily life would once again be tightened in the East Midlands city of more than 300,000 people after a surge in cases.
Speaking in Parliament, health secretary Matt Hancock said cases have continued to rise in Leicester despite a drop nationally.
He said: “The seven-day infection rate in Leicester is 135 cases per 100,000 people, which is three times higher than the next highest city.
“Leicester accounts for around 10 per cent of all positive cases in the country over the past week. And admissions to hospital are between six and 10 per day rather than around one a day at other trusts.”
As of 4pm on Monday, 29 June the infection rate in Leicester was 297.3 with 1,056 confirmed cases, according to Public Health England. In Sheffield, it was 461.1 with 2,686 confirmed cases.
Dr Andrew Lee, a reader of Public Health at Sheffield University, said: “Just looking at the absolute numbers themselves isn’t a good yardstick because it doesn’t show whether the numbers are rising or falling.
“What makes Sheffield different from Leicester is Sheffield’s number started from a very high level, whereas Leicester is the reverse and all of a sudden they had this large rise - basically one quarter of all the cases there happened in the first two weeks of June.”
Leicester City Council reported 944 positive tests in the two weeks of the month to 23 June.
Dr Lee added: “We [in Sheffield] have not had this big surge and our number is the other way round – it’s dropping.”
Mr Hancock told BBC Breakfast work was still being done to understand why Leicester had been so badly affected by the outbreak.
When asked about possible causes such as poverty, higher ethnic diversity, language difficulties and higher-density housing Mr Hancock said they were "familiar" to him.
He added: "We are still doing the work to understand exactly why the outbreak has been so bad in Leicester.
"But lots of the reasons that you mentioned just then are familiar to me and people will find them intuitive."
Mr Hancock said that "of course" the Government was looking at similar places but said the outbreak in Leicester was "very significantly worse" than the next worst hit place.
According to data from the Office for National Statistics, Fir Vale in Sheffield has had the most Covid-19 deaths in the country - nearly twice as many as any other part of England and Wales.
Councillor Mark Jones, whose ward covers the area, cited many of the reasons above for the high number of deaths in the area. Additionally, more than two thirds of the deaths recorded in Fir Vale have been in care homes and not the wider community, NHS officials said.
Dr Lee added: "The thing about the Fir Vale cluster is there was quite a lot constituted in care homes so that gives you an artificial number.”