Why global Covid infections have plummeted

One explanation for the stubbornly high number of infections in Brazil is the role played by new variants, which can spread quickly across the population without a strict lockdown in place to contain them. Similarly in the UK, the B.1.1.7 variant spread rapidly before the current lockdown. Despite recent success in tackling the virus, scientists emphasised that all countries remained vulnerable to surges in new cases. “Any rapid relaxation of protective measures could produce spikes in infection rates,” said Ted Cohen, professor of infectious disease epidemiology at Yale University. “There are large pools of susceptible individuals still at risk.”