Health workers in Brazil’s largest state are begging for help and oxygen supplies after an explosion of Covid deaths and infections that one official compared to a tsunami and said could be linked to a new variant. Amazonas, and particularly its riverside capital Manaus, were pummeled by the epidemic’s first wave last April, when authorities were forced to dig mass graves for victims. But at a press conference on Thursday, the state governor, Wilson Lima, admitted the situation was now even more dramatic and declared an immediate 7pm to 6am curfew to slow the outbreak.