Council and health chiefs have urged Rotherham residents to follow government guidelines as the borough's COVID-19 infection rate more than doubles in a week
The local rate per 100,000 people has increased from of 9.8 cases to 23.
Although the current rate is below that of areas where local lockdowns have been imposed, a further rise would see Rotherham back on the Government's watch list.
The latest data was shared at a meeting of the Rotherham Local Outbreak Engagement Board on September 11. The increase comes as the Government's "rule of six" restrictions come into force, banning people from meeting up with more than six people at a time.
While the Forge Island car park testing site is still open daily, the mobile testing unit at Midland Road is having to close early when national laboratories reach their daily capacity.
Today we are renewing our call to urge people to follow the advice and keep each other safe. We are doing so now because the rate of infections in the borough has more than doubled in the last week, which in turn was an increase on the week before. Over the last couple of months, we have made really good progress moving from one of the highest infection rates, to dropping below national average.
He said: "We have not lost a resident in the borough to COVID for more than a month. That progress has enabled us to begin to reopen many council services.
"And whilst we are fortunately not yet seeing new cases needing hospitalisation, and of course we very much hope it will remain that way, we know that those cases would not necessarily come through for another few weeks.
"The latest information shows we cannot afford to be complacent even for a moment.
"It is also important to note that the evidence continues to suggest that COVID-19 cases are appearing in different parts of the borough; they are not limited to any one area.
"Neither is any particular age group seeming to be most affected. We do need everyone to keep doing their bit to keep Rotherham open."
While Rotherham Hospital has intermittently experienced periods without any COVID-19 positive patients we do expect that we will admit more people who are very sick with COVID-19. As we move into autumn and winter the seasonal pressures of flu will put additional pressures on the system. We urge people to continue to take this pandemic seriously and follow guidelines to try to control the virus.