China’s spiraling Delta variant outbreak has reached Wuhan, the original epicenter of the pandemic, prompting citywide coronavirus testing as authorities scramble to contain the city’s first reported local infections in more than a year.China is grappling with its worst outbreak in months, with more than 300 cases detected in more than two dozen cities across the country. The country now has 144 medium- and high-risk areas, the most since the initial outbreak in early 2020, the National Health Commission said Wednesday.The speed and scale of the spread has spurred mass domestic travel restrictions, with all inter-city coach, taxi and online car hailing services suspended in medium- and high-risk areas. Chinese immigration authorities have also vowed to “strictly restrict non-urgent, unnecessary cross-border travel,” including tightening the issuing of passports for Chinese citizens.On Monday, seven infections were reported among migrant workers in Wuhan, the central Chinese city where the coronavirus was first detected in December 2019. As of Wednesday, a total of 20 local infections have been reported, including 8 asymptomatic cases, according to the Hubei provincial health commission.The city of 11 million people was placed under the world’s first and arguably strictest coronavirus lockdown in January 2020, during the height of its devastating initial outbreak. The paralyzing 76-day lockdown came at a huge personal cost  to residents, but eventually succeeded in taming the virus. Wuhan had not reported any locally transmitted cases since May last year.Despite the initial mishandling, the Chinese government has heralded Wuhan as a success story in its fight against the pandemic. In August 2020, as much of the world grappled with Covid-19, Wuhan made international headlines  when it held an electronic music festival in an open air water park, with thousands of people partying without any masks or social distancing measures in sight.But now, the highly contagious Delta variant has put authorities on high alert.On Tuesday, Wuhan launched a citywide coronavirus testing drive, with residents forming long lines at community testing sites late into the evening. The city has also suspende 17 bus lines and closed a number of subway stations.

The ongoing outbreak first started in Nanjing, Jiangsu province in eastern China, where nine airport cleaners were found to be infected on July 20 during a routine test. Chinese authorities have linked  the cluster to a flight from Russia, which arrived at the Nanjing Lukou International Airport on July 10.”It is believed that the cleaners did not strictly follow anti-epidemic guidelines after cleaning Flight CA910 and contracted the virus as a result. The infection further spread to other colleagues, who are also responsible for cleaning and transporting garbage on both international and domestic flights,” reported  state news agency Xinhua.Since then, the cluster has spread to at least 26 cities, including the tourist hot spot Zhangjiajie and the capital Beijing.In just two weeks, China has reported more than 480 locally transmitted confirmed cases, according to a CNN tally of the National Health Commission’s daily reports.Not all infections have so far been directly linked to the cluster in Nanjing. On Monday, 63 local infections, including 50 asymptomatic cases, were reported in Zhengzhou, the provincial capital of Henan province which was ravaged by deadly floods last month. Most cases are linked to an outbreak at a hospital, where janitors, medical staff and patients are among those infected. The city launched citywide testing Sunday.The fast spreading Delta variant has posed a major challenge to China’s hardline zero Covid strategy, which relies on mass testing, targeted lockdowns, extensive contact tracing and strict quarantine measures to quickly suppress local flare-ups.

China responded by doubling down on its containment approach, adopting stringent measures on a scale not seen in months. Several cities have been placed under effective lockdowns, ordering residents to stay in their homes and canceling flights and trains.The country has also imposed massive nationwide travel restrictions. All provincial authorities have urged citizens not to travel to medium and high-risk areas or leave the provinces where they live unless it is strictly necessary.The Chinese government is particularly concerned about the spread of the virus to Beijing, which is set to hold the Winter Olympics in February next year. The city has reported a handful of cases since last week — its first coronavirus resurgence in months.Beijing authorities have banned people from medium- or high-risk areas from entering, suspending flights, trains and buses from Covid-hit places. Since Tuesday, 23 railway stations have halted ticket sales for train rides heading to the capital, Xinhua reported.Chinese authorities are also tightening restrictions on cross-border travel. China is still largely closed off from the outside world, and those who are allowed to enter are subject to lengthy hotel quarantine.At a press conference Wednesday, an official with the National Immigration Administration said authorities would stop issuing travel documents, such as passports, for Chinese citizens who want to leave China for “non-urgent, unnecessary” reasons. Individuals who need to travel overseas for study, work or business purposes would still be issued travel documents upon approval, he added.