How concerned should we be by the Indian variant?

In recent weeks there has been a lot of new-found optimism in Britain with regards to Covid: case numbers, hospitalisations and deaths have dramatically fallen and the vaccine roll out continues at pace. The virus has now been overtaken as the main cause of death in England and Wales for the first time since autumn. But the pandemic continues to grow, and nowhere more so is this the case than India.

Its hospitals are overrun. Crematoriums are overwhelmed and the first of nine planes from Britain set off on Sunday night to provide oxygen, ventilators and aid. Why should it be surging now? One of the theories behind this explosion is a new variant of coronavirus (B.1.617).

As an epidemiologist and medical academic, I have spent most of my career investigating epidemics and outbreaks of infectious disease. Yet no other disease before Covid has had the ability to shift me from optimism to pessimism and back again as quickly as Covid does.