BEIJING (AP) — The number of new coronavirus cases in an outbreak in China’s northeast tripled Sunday and authorities stepped up anti-disease controls by suspending bus service to Shanghai and ordering residents of another city to stay at home. The case numbers in China’s latest surge of infections are low compared with some other countries. But authorities are enforcing a “zero tolerance” strategy that temporarily shuts down cities to isolate every infected person despite a rising economic cost. The government reported 1,938 new cases on China’s mainland in the 24 hours through midnight Saturday, more than triple the previous day’s total. About three-quarters, or 1,412 cases, were in Jilin province in the northeast, where access to the industrial metropolis of Changchun was suspended on Friday and families were told to stay home after a spate of infections. In Hong Kong, the territory’s government reported 15,789 new cases, down by almost half from Saturday’s total.