THE vast majority of new Covid infections in the UK are being caused by the Delta variant.

Health Secretary Matt Hancock said that 91 per cent of new cases are now due to the fast-spreading strain first found in India.

Mr Hancock revealed the latest official estimate as he gave evidence to Westminster’s Health and Science Select Committee on the government’s handling of the pandemic.

He also disclosed that an initial “reasonable worst case scenario” based on Spanish Flu had predicted that as many as 820,000 Brits could die from the virus.

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It comes as the latest data for Scotland shows that infections have more than quadrupled in a month, although there was no increase in the past 24 hours in the number of patients in hospital with the virus.

Dundee has seen its virus rate more than double in a week to nearly 250 per 100,000 - twice the incidence recorded in Glasgow when the city’s progress into Level Two was first halted in May.

HeraldScotland: Dundee was recording 247 cases per 100,000 by June 7Dundee was recording 247 cases per 100,000 by June 7

HeraldScotland: Dundee City coronavirus rates (Public Health Scotland)Dundee City coronavirus rates (Public Health Scotland)

Dr Hans Kluge, the World Health Organisation’s director for Europe, warned that the Delta variant was “poised to take hold in the region” as many countries prepare to ease restrictions.

He cautioned that it had shown signs of being able to evade some vaccines and that some vulnerable people remain unprotected.

"We have been here before," said Dr Kluge. "Over the course of last summer, cases gradually rose in younger age groups and then moved into older age groups, contributing to a devastating resurgence."

Dr Kluge said that the spike in Covid-19 cases ultimately led to more lockdowns and deaths in the autumn and winter of 2020, adding: "Let's not make that mistake again."

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Professor Neil Ferguson, the epidemiologist whose pandemic modelling was key to ushering in the first UK lockdown, said on Wednesday that estimates of Delta's transmission advantage over the previously dominant Alpha ('Kent') variant have narrowed and "we think 60% is probably the best estimate".

HeraldScotland: Professor Neil FergusonProfessor Neil Ferguson

Previous modelling in May suggested that a variant which was 40-50% more transmissible would be enough for hospitalisations to exceed the first and second waves despite the vaccine rollout, with Prof Ferguson saying it was "well within possibility that we could see another third wave at least comparable in terms of hospitalisations".

However, he added that deaths would "probably be lower" due to the protective effect of the vaccines, but said "there is a lot of uncertainty".

READ MORE: Percentage of Covid cases needing hospital treatment 'has halved'

Earlier this week Nicola Sturgeon said 5% of people who tested positive for the coronavirus in May had gone on to require hospital treatment, compared to around 10% at the beginning of the year, as vaccines weakened the link between infection and serious illness.

The latest data for Scotland shows that there were 5,709 new cases detected in the seven days to June 10, up from 1,335 in the week ending May 10.

The number of patients in hospital with Covid has climbed from 72 to 124 over the same period, with intensive care numbers rising from six to 14.

Five of the 14 ICU patients are in hospitals in Ayrshire - the highest number of any health board.

However, the vast majority of hospital admissions are now being made up by unvaccinated patients under-65 - especially under-50s - who are less likely to become critically ill.

Vaccination figures show that nearly 53% of adults in Scotland have now had both vaccine doses, with 77% having had at least one dose.

HeraldScotland:

However, around 85,000 people aged 16 to 64 in Scotland who are considered "clinically vulnerable" due to pre-existing health conditions remain completely unvaccinated. This equates to around 11% of people in this priority group.

There are also nearly 17,000 people (14%) working in non-care home frontline social care roles who have yet to receive even a single vaccine dose.

This could be due to choice, missing appointments or medical reasons, such as severe allergies.