Since July 20, Xi Jinping’s nation has reported 206 new cases with the epicentre in the city of Nanjing. The outbreak is said to have started when airport workers tested positive after cleaning a plane that arrived from Russia.
In response, all flights from Nanjing airport have been suspended until at least August 11 in a bid to contain the spread of the virus.
While health experts are worried the outbreak may still be in its early state, Chinese state media has called it the “most extensive contagion after Wuhan”.
All 9.3 million of Nanjing’s residents – including those visiting – will be tested, according to state-controlled Xinhua news.
Local officials in the city have said seven of those infected were in a critical condition.
Testing has shown the virus has now spread to at least 13 cities including the capital, Beijing.
Across the Jiangsu province, hundreds of thousands of people have been forced back into lockdown.
Another 41,000 people have been ordered to stay at home across Beijing’s Changping District.
Other provinces such as Sichuan and Liaoning have also reported a spike in new cases as well as the Hunan province.
READ MORE: Seeds of China’s Covid cover-up sown during SARS epidemic
Last week, Beijing rejected the next stage of a World Health Organisation (WHO) plan to investigate the origins of the coronavirus.
The WHO wants to audit laboratories in the area where the virus was first identified.
Zeng Yixin, deputy health minister, said this showed “disrespect for common sense and arrogance towards science”.
Earlier this month, WHO head Dr Tedros Adhanom Ghebreyesus outlined the terms of the inquiry’s next phase.
This included looking at certain science research institutions.
He urged Beijing to “be transparent, to be open and co-operate” with investigators and provide raw patient data that had not been shared during the first probe.
The Delta variant, first identified in India, is more transmissible than the initial pathogen of coronavirus.
According to an internal US Centers for Disease Control presentation, the variant spreads as easily as chickenpox.
There has been a recent surge around the world in cases of the strain, especially in the Asia-Pacific region.
The more transmissible variant has been linked to around half of new cases in Tokyo.