China on Wednesday reported its highest daily number of local coronavirus cases in months as mass testing and contact tracing campaigns uncovered a trail of Delta variant infections.

Health authorities reported 71 domestic cases on Wednesday, the highest since January, as China battles its largest outbreak in months by testing entire cities and locking down millions.

Transmission electron micrograph of SARS-CoV-2 virus particles. File photo: NIAID-RML.

The official results of those tests have revealed a low caseload despite the outbreak spreading to dozens of major cities.

Beijing had previously boasted of its success in crushing Covid-19, allowing the economy to rebound and normal life to return while swathes of the globe struggled to douse a pandemic that has killed more than four million people worldwide.

But the latest outbreak is threatening that record with nearly 500 domestic cases reported since mid-July, when a cluster among airport cleaners in Nanjing, Jiangsu province, was found.

Wuhan, where the virus first emerged in 2019, reported its first local infections in over a year this week and said Tuesday it was “swiftly launching” testing of all 11 million residents.

Hospital in Wuhan. File photo: Wikimedia Commons.

Long lines of residents waited at outdoor testing stations in the summer heat Tuesday, fanning themselves with paper forms while workers in hazmat suits took throat samples.

Meanwhile, Nanjing has tested its 9.2 million residents three times after shutting down gyms and cinemas and closing off residential compounds.

And the tourist destination of Zhangjiajie in central Hunan province, where infected travellers who had been in Nanjing attended a theatre performance, abruptly announced Tuesday that no one would be allowed to exit the city after it emerged as an infection hotspot.

AFP is a global news agency delivering fast, in-depth coverage of the events shaping our world from wars and conflicts to politics, sports, entertainment and the latest breakthroughs in health, science and technology.