Much of Shanghai, China, has been shut down as COVID-19 testing begins in earnest.

On Monday, China began shutting down much of its largest city, Shanghai, as a coronavirus epidemic spreads and doubts about the country’s “zero-COVID” plan are raised. From early Monday until Friday, Shanghai’s financial center and surrounding regions will be closed as part of citywide mass testing. To guarantee that there is no interaction with the outside world, residents will be made to stay at home and deliveries will be placed at checkpoints. Many neighborhoods in the 26-million-strong metropolis have already been shut down, with citizens being forced to take numerous COVID-19 examinations.

On Sunday, Shanghai discovered 3,500 new instances of illness, with all but 50 of them being persons who tested positive but did not display symptoms. Such instances are classified separately from “confirmed cases” in China, resulting in substantially lower totals in daily reporting. Local authorities prefer to adopt a more severe approach, although Communist Party head Xi Jinping has advocated for more targeted actions.