In the country’s largest coronavirus (CCP virus) outbreak in months, Chinese health officials have set up checkpoints and reportedly grounded flights in the eastern city of Nanjing, after an airport cluster in this city is believed to have led to infections in 15 cities across the country in just over a week.

The Nanjing outbreak has infected more than 200 people, including at least 30 in 15 other cities, including Beijing and Chengdu in Sichuan province, Hong Kong-based South China Morning Post reported.

According to the World Health Organization, the highly infectious Delta form is fueling the spread, which has now spread to 132 countries.

Nanjing airport has halted all flights until the middle of August, Global Times reported, citing an anonymous source.

Nanjing authorities began a second round of mass testing for the city’s 9.3 million residents this week.

Anti-virus precautions have been stepped up in other Jiangsu cities, with 18 checkpoints set up on motorways leading into Suzhou to check the health code status of passengers traveling from Nanjing. Suzhou’s road passenger transport between the city and Nanjing has also been halted.

The Nanjing cluster represents at least the third epidemic of the highly virulent Delta type in China, after an outbreak near the Myanmar border in Yunnan earlier this month and another in southerner Guangdong in May–June.

On Tuesday, July 20, nine instances were discovered, all among Nanjing airport employees. The following day, another 24 local cases were reported, bringing the total number of infections linked to the cluster to 171.

People who joined a crowd of 2,000 during a show in Zhangjiajie, Hunan, on July 22nd are among the newly verified cases.

All of the attendees, who are now dispersed around China, have been classified as “high risk.” People from Dalian and Chengdu who had been diagnosed since then reportedly attended the show, with some flying in from Nanjing’s Lukou international airport.

Much of the attention is focused on the airport, where cleaners who were cleaning planes that had arrived from abroad and domestic flights acquired the illness and spread it to their coworkers and families.

The airport did not divide cleaning workers responsible for foreign flights from those responsible for domestic flights, exposing a major lack of day-to-day monitoring, the Commission for Discipline Inspection, China’s top anti-corruption body, said in a website statement on Wednesday. According to the statement, the virus was imported and disseminated in China because international and domestic aviation operations were jumbled together.

Covid-19 guidelines for flights and airports have been established by China’s Civil Aviation Administration, which prohibit service employees on foreign flights from utilizing public facilities accessible to passengers. For domestic flights, they must also avoid contact with service personnel.

On July 23, Feng Jun, the chairman of Eastern Airport Group, which manages Nanjing’s airport, was suspended due to the epidemic.