More than a year and a half after the coronavirus was first detected in China — followed by the world's first big wave of COVID-19 — the country is again battling to stem the spread of new cases attributed to the more infectious delta variant of the virus.

The latest outbreak was first discovered in the eastern city of Nanjing, in the coastal province of Jiangsu south of the capital, Beijing. In the past week, it has quickly spread to 15 cities across the country, the South China Morning Post reports.

In the most recent outbreak, the first case was detected on July 20 in a passenger arriving from Russia at the international airport in Nanjing — a city of more than 9 million. Since then, at least 184 new infections have been found, Reuters reports.

"The number of cases reported has climbed recently," deputy director general of the Nanjing Centre for Disease Control and Prevention Ding Jie said on Tuesday, the South China Morning Post reported. "Early cases transmitted among aircraft cabin cleaners quickly and spread further through social activities and work environment contamination."

"We tracked down a large number of close contacts and have been testing them. New cases are constantly being discovered," Ding said.

All flights from Nanjing have been canceled until Aug. 11, the Communist Party-controlled Global Times said earlier this week. It said the number of flights in and out of the city had been reduced since Monday.

The latest outbreak "may prove to be of a larger scale than the previous outbreak in Guangzhou, South China's Guangdong Province" that first hit in May, the Global Times reported.

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