A COVID-19 flare-up in the Chinese city of Nanjing has spread to more cities and provinces, including Wuhan, where officials ordered mass testing for nearly 12 million of the city's residents.China is among several Asian nations battling a virus resurgence, along with Japan, where one of the country's top doctors called for government officials to impose a national state of emergency.China tracking COVID clusters in multiple citiesA quickly evolving Delta (B1617.2) outbreak that began in Nanjing, the capital of Jiangsu province on China's east-central coast, has now triggered clusters in at least 30 cities, up from 13 cities last week, according to the Washington Post.Yesterday, officials in Wuhan reported three Delta variant cases, marking