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’.