The scale of the humanitarian crisis in Gaza — and the difficulties faced by aid workers responding to it — goes “beyond what has been seen before” in other conflicts, the United Nations said on Wednesday. The cost of addressing it may be similarly staggering. The U.N. said its agencies and other aid groups would need more than $2.8 billion …

In 2009, long before Jeff Yass became a Republican megadonor, his firm, Susquehanna International Group, invested in a Chinese real estate start-up that boasted a sophisticated search algorithm. The company, 99Fang, promised to help buyers find their perfect homes. Behind the scenes, employees of a Chinese subsidiary of Mr. Yass’s firm were so deeply involved, records show, that they conceived …

In the early days of the Covid pandemic, a team of scientists called on the World Health Organization to acknowledge that the disease could spread through the air. Initially, the agency rebuffed them, despite growing evidence that coronavirus-laden droplets stuck around in the air, making indoor spaces hotbeds of infection. The researchers responded with a public campaign, which helped persuade …