BEIJING—China’s worst coronavirus outbreak since the start of the pandemic a year-and-a-half ago escalated Wednesday with more cases around the country, the sealing-off of one city, and the punishment of its local leaders. The country is now on high alert as an outbreak of cases connected to the international airport in the eastern city of Nanjing, Jiangsu province, affected at least 17 provinces. China reported on Wednesday the most new locally transmitted COVID-19 cases since January. The exact number of new cases is not known since the Chinese regime routinely suppresses or alters information. In Wuhan, the central city where the first cases of COVID-19 were identified in late 2019, mass testing has shown some of its newly reported cases have a high degree of similarity to cases discovered in Jiangsu province. Those cases have been identified as being caused by the Delta variant that first was identified in India. …