The new variant: a note on the evidence

Boris Johnson introduced a third lockdown last night after an assessment by Britain’s four chief medical officers that the NHS wouldn’t be able to cope within three weeks on present trends. ‘Cases are rising almost everywhere, in much of the country driven by the new, more transmissible, variant,’ the medical officers said in a statement. With Covid caseloads clearly rising in hospitals nationwide, the grounds for action are pretty clear. But how sure can we be that the new variant is to blame? 

One question seems to be asked again and again: if the new Covid variant is much more transmissible, why isn’t it rising everywhere? Why just in London and the South East? Why lock down the rest of the country if there’s no sign of hospitals being inundated or things out of control in the rest of England? There are two answers to that: one technical, one more straightforward.