In China, most people have never been exposed to the coronavirus. Could the COVID-19 surge in China unleash a new coronavirus mutant on the world? Scientists don't know but worry that might happen. It could be similar to omicron variants circulating there now. It could be a combination of strains. Or something entirely different, they say. "China has a population that is very large and there's limited immunity. And that seems to be the setting in which we may see an explosion of a new variant," said Dr. Stuart Campbell Ray, an infectious disease expert at Johns Hopkins University. Every...