The latest Public Health England (PHE) data, published today, shows 640 people in Leeds have tested positive for the variant so far. That is up from just 24 the week before.
Leeds now has more confirmed cases than several areas of the country where surge testing has already been rolled out, including Bradford (524), Calderdale (190), Sefton (291) and Reading (248)
Only 10 other areas of the country have recorded more cases of the variant, which was first detected in India and now makes up more than 90 per cent of the new Covid-19 cases in the UK.
Leeds City Council states hospitalisations and deaths remain low, but cases of Covid-19 have risen "among unvaccinated age groups" and the city's infection rate has risen by 81 per cent over the past week, to 82.2 per 100,000.
Councillor James Lewis, leader of Leeds City Council, said: “With restrictions changing and more people getting out and enjoying Leeds coupled with the increased prominence of the Delta variant, we have inevitably seen a rise in cases over these past few weeks.
“What remains key is that we are able to stay ahead of that spread and to make sure people in Leeds of all ages stay safe and informed. We are confident that locally, we have a robust and resilient network of partners, all working together to respond quickly and efficiently to this rise in cases among young people and to keep on top of any clusters.
“A good supply of vaccine is key to all of this, so we are constantly pushing to ensure our supply levels remain strong and meet our needs locally. We need the national vaccine response to continue to match the level of care and diligence we have here in Leeds.”
Over the last week, the number of cases of the variant has risen from 29,892 to 42,323 and evidence suggests it is 60 per cent more transmissible than the Alpha variant, which was first detected in Kent in September 2020.
PHE states the recent rise in cases “is not yet accompanied by a similarly large increase in hospitalisations” and the latest data suggests the vaccine roll out “continues to mitigate the impact of this variant”.
Government figures show Leeds Teaching Hospitals NHS Trust staff were treating just 10 people for the virus on June 8.
In neighbouring Wakefield, where 308 cases of the Delta variant have been identified, public health experts stepped up testing earlier this month
Anna Hartley, Wakefield Council’s Director of Public Health, said: “Cases of the Covid-19 Delta variant continue to rise across the Wakefield district.
"We are actively monitoring the situation and taking all necessary action. “We have increased testing capacity and continue to promote vaccination in areas experiencing cases of the Delta variant through proactive measures including community door knocking and drop-in vaccination sessions."
Dr Jenny Harries, chief executive of the UK Health Security Agency, said cases of the variant are "on the rise across the country" and vaccinations are still the "best defence".
“If you are eligible, we urge you to come forward and be vaccinated," she added.
“Remember that two doses provide significantly more protection than a single dose. However, while vaccination reduces the risk of severe disease, it does not eliminate it.
“With data showing that Delta is significantly more transmissible than Alpha, it is just as important as ever to follow public health advice, which has not changed."
The Department of Health and Social Care did not comment on the recent spike in Leeds, but said all surge testing updates are published on its website.