US President Donald Trump threatened to cut ties with China over its role in the spread of the coronavirus, as the global death toll from the disease topped 300,000. Despite fears of a second wave of infections, national and local governments around the world are easing lockdown orders as they try to get stalled economies moving again. But there were warnings Friday that some of the world’s poorest people remain the most vulnerable, with predictions that a quarter of a billion Africans could be infected without urgent action. The nexus of poverty and risk was highlighted by the discovery of cases in the world’s biggest refugee camp, where upwards of a million Rohingya live in squalor. “We are looking at the very real prospect that thousands of people may die from COVID-19” in these camps, ...