The emergence of dozens of new coronavirus cases around a northeastern Chinese city has prompted authorities to lock down the area and replace some officials, initiating a limited return to strict controls at a time when the government is trying to spur economic activity. Residents in some parts of Jilin province are being ordered to stay home, and traffic into and out of some localities is being curtailed in an effort to prevent the virus that causes Covid-19 from spreading, according to government notices, state media and…