About 250,000 people would have died in the UK under the government’s previous strategy for dealing with the coronavirus crisis, even if the health service was able to cope with the surge in illnesss, according to Imperial College researchers.

Boris Johnson announced stringent new measures — including social distancing of the whole population — on Monday after modelling from Imperial College warned the government’s previous, more measured, approach would have overwhelmed hospitals with demand for intensive care beds.

The new coronavirus strategy could cut UK deaths from Covid-19 to “a few thousands or tens of thousands” through to the autumn, but the researchers questioned whether such extraordinary restrictions could be sustained beyond that point.

“We might be living in a very different world for a year or more,” said Neil Ferguson, head of the modelling programme at Imperial’s MRC centre for global infectious disease analysis.

Imperial’s researchers presented their latest analysis after the prime minister’s press conference at 10 Downing Street on Monday. Modelling a scenario similar to the new measures — including social distancing of the whole population, home isolation of cases and household quarantine of their families — might bring total deaths down to about 20,000 if they were observed strictly, said Azra Ghani, a member of the Imperial team.

School closures might become necessary too, though they could seriously harm the NHS by forcing staff to stay at home to look after their children. As many as a third of nurses have school-age children, Prof Ferguson said.

Michael Head, senior research fellow in global health at the University of Southampton, who was not involved in the project, commented: “The modelling paper by Imperial College London has clearly informed the new measures from the chief medical officer, and therefore it is excellent to have that data available to scrutinise.

“Prof Ferguson and colleagues clearly warn that the NHS will at some point likely be overwhelmed, and thus perhaps today’s announcements will hit home to the UK general population just how serious this pandemic is, and what will be required of them over the coming months,” Dr Head said.

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According to Prof Ferguson, the new strategy abandons the idea of “herd immunity” — managing the infection rate so that enough people become immune to prevent the virus from transmitting. The new aim is suppression. “We want to ensure that only a small fraction of the country will be infected,” he said.

Even with the most effective so-called “mitigation strategy” and under the assumption that all patients are fully treated, the paper concludes there would be around 250,000 deaths in the UK and up to 1.2m deaths in the US.

It would be harder than experts believed last week to prevent hospitals from becoming overwhelmed by Covid-19 patients, Prof Ferguson said: “We have had bad news from Italy and from early experience in UK hospitals that the intensive care requirements will be nearly twice what we had anticipated.”

The latest evidence suggests that 30 per cent of patients admitted to hospital with Covid-19 will need critical care in an intensive care unit, he said. Previous estimates, based on experience with viral pneumonia, were too low.

Critical care bed demand would be eight times capacity after mitigation measures were applied, and around 30 times capacity in both the US and UK in an “uncontrolled epidemic”.

The Imperial College paper concludes: “The major challenge of suppression is that this type of intensive intervention package — or something equivalently effective at reducing transmission — will need to be maintained until a vaccine becomes available (potentially 18 months or more), given that we predict that transmission will quickly rebound if interventions are relaxed.

“Intermittent social distancing — triggered by trends in disease surveillance — may allow interventions to be relaxed temporarily in relatively short time windows but measures will need to be reintroduced if or when case numbers rebound.”

Letter in response to this article: It is right to take scientific advice seriously / From Sir Anthony Brenton, Cambridge, UK

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