A health official said that nucleic acid testing should be done accurately not only to avoid the imposition of excessive anti-COVID measures, but also to cover all individuals at potential risk of infection.

Shen Hongbing, deputy head of the National Disease Control Administration, told a news conference on Thursday that mass nucleic acid testing will no longer be undertaken in administrative regions where just a few people have been infected, and where the chain of transmission is clear and does not risk community transmission.

However, if an assessment suggests there is chance the epidemic may spread, the area in question should test all residents once a day. If, after three days there are no cases of social infection, a further three mass tests should be carried out and then stopped if there is no indication of infection, he said.

Meanwhile, local governments are to strictly implement nucleic acid testing for key personnel in positions of high risk, he said.

"Affected departments should continue to test key personnel. However, the scope of nucleic acid testing should not be expanded randomly," he said.