Young people living in Leeds have been warned to take responsibility for their actions as coronavirus infection rates continue to rise.
The city has been added to Public Health England's weekly watch list of areas of concern, following an increase in cases over the previous weeks.
The city council said many of the cases are in different areas, meaning they may be linked to social interaction and leisure activities.
It said the spread is "broad and changeable across wards", with increasing numbers detected in young people sparking concerns over close-contact activities like house parties.
Leeds City Council issued eight £10,000 fines last weekend against organisers of illegal raves and music events.
Council leader and chair of the outbreak control board, Judith Blake, urged young people to "Think carefully about your actions. The virus is showing an increase in cases for 18 to 34 year olds. This is the place where the virus is most active at the moment."
"This is a pivotal moment in our efforts to control the spread of the virus in Leeds and to keep our city open.
"Nobody wants to see further restrictions on life in Leeds and we want to assure everyone that we're doing absolutely everything within our power to avoid that happening.
"But the harsh reality is that if our infection rate continues to rise as it has been, we will be left with no alternative.
"With that in mind, now more than ever we need a collective effort from the people of Leeds who have shown so much resilience and civic pride throughout this crisis.
"It's up to us all to keep our families, friends and neighbours safe and to play our part in keeping Leeds's recovery going."
The latest seven-day infection rate shows Leeds as having 29.4 cases per 100,000 people, with 44 new cases today identified on Wednesday and a testing positivity rate of 4.2%.
Leeds West MP Rachel Reeves tweeted that it was "vital" people observed social distancing rules.
The city council has said that while being on the list would not mean further restrictions would be brought in at this stage, it would mean increased monitoring of cases and could see additional steps taken in the future.
Meanwhile gyms and leisure facilities will be allowed to reopen in Bradford next week as coronavirus restrictions are further eased in West Yorkshire.
Indoor swimming pools, including water parks, indoor fitness and dance studios, indoor gyms and sports courts and facilities will be able to lawfully reopen from Tuesday 8th September 00.01
Casinos, skating rinks, bowling alleys, exhibition halls, conference centres, and indoor play areas (including soft play areas) will be able to lawfully reopen from Tuesday 8 September 00.01 across West Yorkshire
Socially distanced indoor performances will also be able to resume, and remaining restrictions on certain close contact services (treatments on the face, such as eyebrow threading or make-up application) will be lifted across West Yorkshire.
In terms of the 'areas of concern', Leeds has been added to the list but Newark & Sherwood and Wakefield have been removed.
The ban social gatherings in homes and gardens in parts of West Yorkshire will remain in place for at least another week. This includes urban areas of Bradford, Dewsbury and Batley in Kirklees and some parts of Calderdale. A further announcement following a review will be made next Friday.
From 2 September local restrictions will be relaxed in nine of Bradford's 30 wards.
Bradford wards which will no longer be subject to local restrictions from Wednesday 2 September:
Craven, Ilkley, Worth Valley, Baildon, Bingley, Bingley Rural, Shipley, Wharfedale, Windhill & Wrose
Bradford wards which will still be subject to local restrictions:
Bolton and Undercliffe, Bowling and Barkerend, Bradford Moor, City, Clayton and Fairweather Green, Eccleshill, Great Horton, Heaton, Idle and Thackley, Keighley Central, Keighley East Ward, Keighley West, Little Horton, Manningham, Queensbury, Royds, Thornton and Allerton, Toller, Tong, Wibsey, Wyke
Click here to check your postcode via Bradford Council's website.
Local restrictions will remain in place for Dewsbury and Batley where rates of Covid-19 are higher.
Kirklees wards which will no longer be subject to local restrictions from Wednesday 2 September:
Almondbury, Ashbrow, Birstall and Birkenshaw, Cleckheaton, Colne Valley, Crosland Moor and Netherton, Dalton, Denby Dale, Golcar, Greenhead, Heckmondwike, Holme Valley North, Holme Valley South, Kirkburton, Lindley, Liversedge and Gomersal, Mirfield, Newsome
Kirklees wards which will still be subject to local restrictions:
Batley East, Batley West, Dewsbury East, Dewsbury South, Dewsbury West
Click here to check your postcode via Kirklees Council's website.
In Calderdale, Halifax wards will remain under local restrictions, while wards in the Calder Valley will no longer have to follow local restrictions.
Calderdale wards which will no longer be subject to local restrictions from Wednesday 2 September:
Brighouse, Calder, Elland, Greetland and Stainland, Hipperholme and Lightcliffe, Luddendenfoot, Rastrick, Ryburn, Todmorden
Calderdale wards which will still be subject to local restrictions:
Illingworth and Mixenden, Northowram and shelf, Ovenden, Park, Skircoat, Sowerby Bridge, Town, Warley
Click here to check your postcode via Calderdale Council's website.