Mass testing is underway as China experiences its worst COVID-19 outbreak since the pandemic started according to the Associated Press. The outbreak led to one Chinese city being sealed. The raw video above shows mass testing sites in Wuhan where the virus was first detected and in Zhengzou.

The outbreak is spreading across 17 Chinese provinces. More than half of the new cases reported Wednesday are in Jiangsu province. Its capital city is Nanjing which is where the airport is located.

Mass testing in Wuhan found some of its recent cases are very similar to cases discovered in Jiangsu province, which have been identified as Delta variant cases.

While it is the worst outbreak in more than a year, the overall number of cases is underwhelming with only 71 new cases of local transmission reported Wednesday. In addition, 25 travelers from overseas have COVID-19 and have entered quarantine. That makes Wednesday’s total 96 new cases. The National Health Commission said 15 of those people were asymptomatic.

Far higher numbers were reported in Yangzhou, a city next to Nanjing. The city had recorded 126 cases as of Tuesday.

China’s people had lived virtually free of the virus over the last year. Strict border controls, distancing, and quarantine measures, stamped out any small flareups when the happened.

Last week, China’s National Immigration Administration announced they were suspending issuance of passports to all travelers except for those with an urgent need.

Another COVID-19 hotspot has emerged in the city of Zhangjiajie. The city itself has only recorded 19 cases since last week. However, Shanghai government-owned newspaper reported individual cases linked to Zhangjiajie’s outbreak have spread to at least five provinces.

The city of about 1.5 million ordered residential communities to seal Sunday. The order prevented people from leaving their homes. On Tuesday, officials said no one, whether tourist or resident, could leave the city.

In addition, the city government’s Communist Party disciplinary committee issued a list of local officials who “had a negative impact” on pandemic prevention and control Wednesday. Those officials would be punished.