The key phrase we all need to understand is “herd immunity” – which is what happens to a group of people or animals when they develop sufficient antibodies to be resistant to a disease.
The strategy of the British government in minimising the impact of Covid-19 is to allow the virus to pass through the entire population so that we acquire herd immunity, but at a much delayed speed so that those who suffer the most acute symptoms are able to receive the medical support they need, and such that the health service is not overwhelmed and crushed by the sheer number of cases it has to treat at any one time.
The government’s experts – the chief medical officer and the chief scientific advisor – have made two big judgements.
First, as the World Health Organisation on Wednesday in effect conceded, that there is no way now of preventing the virus sweeping across Africa, Asia and the Americas – which in practice means that it will be an ever-present threat to the UK, unless and until a mass vaccine is available for use.
Second, the kind of coercive measures employed by China in Wuhan and Hubei have simply locked the virus behind the closed doors of people’s homes.
And just as soon as the constraints on freedom of movement are lifted there, the monstrous virus will rear its hideous face again.
What are the consequences for the UK of these judgements, which the Prime Minister and Health Secretary are accepting?
We will know the detail later on Thursday, after the Cobra meeting of ministers and experts make the formal decision to move from the phase of containing the virus to delaying the inevitable epidemic.
But we already know that at the heart of their plans are increasing the proportion of the population able to be tested and also what’s known as “social distancing”.
In the first instance, this will mean encouraging anyone showing even the mild symptoms – such as a dry cough – to self-isolate at home.
But what it does not mean, at least yet, is school closures or the banning of mass events like football matches.
There are a few reasons why school closures are not regarded as sensible, not least that children themselves are the least at risk from the virus – although they may well be an important channel of infection-transmission to older people who are at risk.
However, the government’s main argument against closing schools is it would – at a stroke – massively deplete the manpower of hospitals and care homes, because vast numbers of medical staff would be forced to stay home to look after their children.
And at the heart of the UK’s challenge – as confirmed on Wednesday in the Budget with its extra £5 billion for the NHS, as a down payment on the needed extra beds and relevant kit – is how to make sure hospitals have the resources to treat the expected surge in those needing urgent attention.
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For what it’s worth, ministers are looking with grim bemusement at the debate in football’s governing bodies about banning the public from stadia.
They fear this fuels alarmism and do not think playing matches behind closed doors is necessary at this stage.
Far more sensible, they believe, is for all of us to become much more wary about physical contact with everyone in our day-to-day lives – whether travelling to work, at work, or at the shops.
And many more of us should take the opportunity to work at home, perhaps all the time, if we possibly can.
To get through this, we all need to become less tactile, more cautious in our physical contact.
And, as the WHO’s Margaret Harris said on my show last night, these social and cultural changes may have to become permanent.