The airport in Nanjing city can destroy more than 500 flights on July 21, after detecting nearly 20 Covid-19 cases.

Nanjing City Health Employees, Jiangsu Province said they discovered the outbreak of sanitary workers at Nanjing Loc Loc International Airport through periodic testing.

17 Patients are a cleaning staff at the airport, mainly working at the airport and on airplanes, so they may be related to the imported infection, Fang Zhongyou, the manager of Nanjing Health Commission,

People queue for Covid-19 testing in Nanjing City on July 21.

Officials said the city was preparing to test Covid-19 for 9 million people.

Xu Yong, Eastern Airport Group, airport management unit, said all employees were asked to not leave the airport after the test, while those who are resting are also required to return to the airport

Before the test results, all parts will take the most stringent measures and all employees must wear protective clothes at work, he said, adding only some convenience stores in the yard

Deputy Mayor Hu Wanjin also said more than 20,000 residents near high-risk areas are required to be limited.

Jin Dong-yan, the molecular virus at Hong Kong University, said that the cluster in Nanjing showed that the effort to open China's border to be more cautious.