World health officials are scrambling to determine just how widespread the new coronavirus is as Chinese authorities reported a surge in new cases overnight after changing how it counts confirmed infections.

“How big is the iceberg?” Dr. Mike Ryan, executive director of the World Health Organization’s emergencies program, said at a news conference at the agency’s headquarters in Geneva. “We do know, and we all accept, that there is transmission occurring at some level in communities. We’ve all seen those clusters, we’ve…