Chinese authorities reported 1,337 locally transmitted cases of COVID-19 across dozens of mainland cities Monday as the fast-spreading variant commonly known as “stealth omicron” fuels China's biggest outbreak in two years. The vast majority of the new cases were in far northeastern Jilin province with 895. Shenzhen reported 75 new cases as residents began the first of three rounds of mass testing. Officials on Sunday locked down the city, which has 17.5 million people and is a major tech and finance hub that neighbours Hong Kong.