CLAIMS that up to 80 per cent of Scotland's population could contract coronavirus are "not a realistic estimate", one of Scotland's leading infection scientists has said.

Professor Hugh Pennington, emeritus professor of bacteriology at Aberdeen University, said the predictions were based on a scenario of widespread human-to-human transmission where "we just let the virus run" without any attempt to contain it.

The Scottish Government said on Monday that a "reasonable worst case scenario" could see 50 to 80% of the population contract the strain, known a Covid-19.

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Prof Pennington said: "It's not a realistic estimate.

"The worst case scenario is definitely the worst case scenario: it means that everything that could go wrong does go wrong, with absolutely no containment measures in place.

"The mathematical models have shown that the spread of the virus will be very severely restricted if we 'lock up' people who have been in contact with it - self-isolation so to speak - or we take all the patients who've definitely got symptoms and we put them in hospital, because that's another form of isolation, in effect.

"The people who we've really got to worry about are healthcare workers which has always been a problem, because the super spreaders are the ones who are coughing and spluttering and they're the ones most likely to end up in hospital."

The Scottish Government says a peak outbreak could see 80% of Scotland's 5.4 million population infected, with 4% of this group requiring hospitalisation - around 170,000 people.

The estimate is in line with World Health Organisation data which analysed more than 44,600 cases in China and found that 80% of patients developed mild symptoms such as a cough, fever or runny nose, but around 5% became critically ill with complications such as respiratory failure, septic shock, or organ failure.

The risk was particularly high among older people, especially over 80s, and in patients with diabetes, high blood pressure, and heart or lung conditions.

Alarmingly, mortality among the critically ill has also been running at more than 50%, according to the WHO.

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In a "worst-case scenario" Scotland where 4.35m become infected, that would translate to 217,000 critically ill and more than 100,000 dead.

To put that into context, NHS Scotland has only 13,105 acute hospital beds and the worst winter flu season in recent years claimed around 13,000 lives across the whole of the UK.

In 2018 - the most recent year for which data is available - a total of 16,153 people died in Scotland from all forms of cancer.

However, scrutiny of the latest figures for Hubei, the Chinese province where the virus first originated in December, shows that there have been 67,103 confirmed cases in a population of just over 59m - an incidence rate of 0.1%.

In China as a whole, there are now 80,303 confirmed cases of Covid-19 in a population of over 1.4 billion - equivalent to six per 100,000 people - while in Italy, which has the third highest prevalence of the virus in the world, there are three cases for every 100,000 people.

Professor Rowland Kao, chair of veterinary epidemiology and data science at University of Edinburgh’s Roslin Institute, said: "I think what it comes down to is that when we talk about worst case scenarios, the implication is 'when you do nothing to stop it'.

"Now of course in Hubei they've done everything they can to stop it. Probably more than anyone else in the world.

"Politically, China is obviously much better placed to put up very stringent controls. So the number they have is partially due to that response."

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A WHO report published on Friday February 28 credited China's "aggressive response" for curtailing the spread of the virus.

The number of new cases peaked in early February and has been slowing ever since, while transmission has escalated in the rest of the world.

The WHO report said China had "rolled out perhaps the most ambitious, agile, and aggressive disease containment effort in history", and in doing so "has changed the course of a rapidly escalating and deadly epidemic”.

Interventions included the lockdown of Wuhan - the city at the centre of the outbreak - and nearby cities in Hubei province.

Elsewhere in China people voluntarily quarantined themselves with their compliance monitored by appointed neighbourhood leaders.

Two new dedicated hospitals were built in Wuhan within a week - with many of the beds now lying empty - and aggressive "social distancing" measures were implemented, such as cancelling sporting fixtures, closing theatres and cinemas, and extending the Chinese New Year school holidays.

WHO scientists who visited hospitals, railway stations, food markets, and other public spaces described "a sense of responsibility and collective action...there’s war footing to get things done”.

In Western democracies, such stringent controls and cooperation are harder to imagine, but the UK government's battle plan includes potential measures such as school closures, putting the Army on standby to help fill gaps in emergency services arising from an outbreak, giving health boards the power to detain people with the virus and stop them from travelling, or forcing those suspected of having the virus to be tested and quarantined under court order.

Professor Kao believes the 50-80% figure for 'peak' outbreak in the UK has probably been extrapolated using something called the "basic reproduction number", a theoretical model used by scientists to predict the limits of an outbreak.

He added: "It's a funny thing because you want to motivate people enough to listen, but you don't want to scare them.

"You want them to do the things that are sensible. If people don't take it seriously, they're pretty much going to go about their daily business.

"That includes people who are a little bit sick still going to work, or still sending their kids to school.

"So what you're trying to do is say 'look, if we actually do nothing, these are the kinds of numbers we could end up with'."

A Scottish Government spokesman said: “A ‘reasonable worst case scenario’ would be that 50-80% of the population might become infected. But in this case, a large proportion of the infected population are likely to show no symptoms.

However, as more data becomes available from around the world this will allow modellers to give us increasingly accurate estimates."