Brazil's Covid-19 case numbers and deaths have hit staggering new highs in the past month: over 60,000 died in March alone. Now it is facing a political crisis to match its health crisis. President Jair Bolsonaro, his authority undermined by the raging pandemic, sacked his defence minister and three top military chiefs in what looks like a struggle for control over the armed forces. Tom Hennigan in Sao Paolo reports.