ONE in five patients admitted to hospital with Covid since the start of August have been aged under 45, with teenagers among those requiring acute care.

Nicola Sturgeon said the figures should be a reminder to younger Scots that the virus can cause serious illness, but stressed there are now “warning signs flashing” that Scotland is on the verge of an exponential rise in hospital admissions amid an increase in the number of infections among older and more vulnerable Scots.

With Prime Minister Boris Johnson urged to convene a meeting of the Cobra emergency committee this weekend, the First Minister said the coming days “are likely to see some hard but necessary decisions”.

“If we want to avoid another full-scale lockdown, which all of us do, doing nothing almost certainly isn’t an option,” said Ms Sturgeon.

On Thursday the largest regional lockdown so far in the UK - covering Newcastle, County Durham, Sunderland and the rest of northeast England - saw all bars, pubs, restaurants, cafes, cinemas and other leisure venues forced to close between 10pm and 5am.

READ MORE: Two week 'circuit breaker' lockdown could halve new infections 

From Tuesday, Merseyside, Warrington, Halton and Lancashire - excluding Blackpool and Greater Manchester - will face the same hospitality curfews, amid rumblings that a new national lockdown could be looming.

It comes as data obtained by the Herald from Public Health Scotland shows that younger Scots have made up a higher proportion of recent hospital admissions for Covid.

The Herald: Scotland hospital admissions for Covid up to September 9 (PHS)Scotland hospital admissions for Covid up to September 9 (PHS)

Over the initial phase of the pandemic, up until August 5, people aged 45 and under accounted for just 526 (9%) of the 5953 Covid admissions.

These were individuals who had tested positive on, or within the 14 days prior to, hospital admission.

The data is therefore unaffected by recent changes to how hospital patients with Covid are counted.

However, in the four weeks to September 9 - the last date for which data is available - people aged under 45 accounted for 15 (21%) of the 70 new Covid admissions.

These included nine patients aged 25 to 44, as well as two teenagers between the ages of 15 and 19, one person aged 20 to 24, and three patients aged from infants to 14 years old.

There were also two admissions to intensive care for Covid patients aged 15 to 44.

Professor Jason Leitch, Scotland’s national clinical director, said the trend fitted with evidence that a resurgence in coronavirus infections had initially emerged in the younger population, leading to a crackdown on house parties and curbs on the size of groups allowed to socialise together.

Prof Leitch said: “That would fit with the pattern of disease we’re seeing right across the UK and Europe.

“That when the virus was at its previous peak, it affected all ages and particularly the vulnerable - therefore the group who were under 45 was proportionately smaller.

“The proportion of 21% [in the past month] makes perfect sense to me because that’s the group who are getting the infection in the last few weeks.

“Unfortunately it will not stay in that group because we know [the virus] moves in incubation chunks of two weeks at a time, so it will move into older populations unless you do something.

“And the two things that you can do are Test and Protect and human behaviour.”

Prof Leitch added: “Let’s be clear, people in their 20s have died of this disease. It’s not that you’re immune because you’re young.

“You’re much, much more at risk if you’re old - but you’re not immune if you’re young.”

READ MORE: Study reveals patients most likely to develop 'long-Covid' - with surprising results 

Despite the shift, older Scots continue to outnumber the young overall for Covid admissions.

Between August 5 and September 9, there were 31 admissions for over-65s and 24 in those aged 45 to 64.

The total number of people in hospital who have tested positive for Covid in the past 28 days also continues to rise, climbing from 48 on Tuesday - when the counting method was revised - to 61 yesterday.

Previously the daily figure for ‘people in hospital with Covid’ could include patients who had tested positive for the virus in the past, recovered, and who were actually being treated for an unrelated condition.

The First Minister said she was unable to provide detail on the age breakdown for the 61 patients currently in hospital, but warned that Scotland is on a similar trajectory to England and France unless transmission of the virus can be curtailed.

“We are seeing a rise in hospital admissions,” said Ms Sturgeon.

“We are not yet seeing that in Scotland to the same extent a England, but we would expect it’s just a matter of time if we don’t interrupt things.

"There is also a sign that it's not just older people who are being admitted to hospital - some in the younger age group are also among the hospital admissions, which is a reminder that while younger people are less likely to get ill, they can get ill.

"On every aspect of our data right now, there are warning signs flashing. That has to prompt us to take action."

READ MORE: Real number of Covid patient in hospital in Scotland slashed to 48 after 'overcounting' controversy

In France, deaths from Covid have doubled from fewer than 100 per week in mid-March to 230 a week now, with weekly hospital admissions also tripling over the same period from around 1000 a week to more than 3,200 in the past week.

The Herald:

In England, the number of people being admitted to hospital with Covid has also been climbing rapidly, going from 84 on September 7 to 194 on September 15.

The Herald:

In Scotland, the percentage positivity - the number of positive Covid swabs for ever 100 people newly tested - reached 4.4% yesterday, the highest single day result since May.

This is a key marker of whether an epidemic is under control.

According to the World Health Organisation, if a country has a comprehensive testing regime in place and 5% of samples continue to return a positive result over a two week period, the prevalence of the virus has become unsafe and is beginning to spread out of control.

Once the 5% tipping point is reached, a return to lockdown - in some form - is advised.

In the past week, the number of people tested for Covid in Scotland has slumped to just under 44,000 - compared to nearly 100,000 at the end of August - but 3.6% of those swabs were positive.

The reproductive spread of the virus - or 'R number' - is also estimated to be between 1.1 and 1.5, indicating that every 100 infectious people will pass it on to between 110 and 150 others.

"The bottom line here is that the virus is on the rise again," said Ms Sturgeon.

"Our case numbers are not yet rising as fast as they were back in March.

"But they are rising again and they are rising quite rapidly.

"The percentage of tests coming back positive is also not anywhere near as high as it was back in March, but again it is rising.

"And as I reported [on Thursday], the R number we believe is now above one.

"Across the UK, and this is particularly the case in England right now, hospital admissions are rising. ICU admissions are rising too.

"While this is particularly the case in England right now, this should sound a warning signal for us here in Scotland too.

"And, while for the last few weeks, people might have taken comfort from the low levels of older, more vulnerable people contracting the virus, I have to say to you that picture is also beginning to change.

"Recent data shows that the percentage of cases in the older population is now beginning to rise as well.

"Looking more widely, we can observe that in broad terms we might now be, at an earlier stage, on a similar path to that which has been taken in recent weeks by France.

"About four weeks ago, France stood broadly where we do today.

"But now they face around 10,000 new cases per day and hundreds of people in ICU and deaths in France are already rising now as well.

"So our task is to make sure – if we can – that we interrupt that, and we don’t end up where they are now.

"What lies behind this is a simple reality: we are facing the risk again of exponential growth in Covid."