Shanghai will launch another round of citywide nucleic acid testing on Tuesday to continue screening out positive COVID-19 cases, with the goal of soon achieving zero community transmissions.Every resident in the city's locked-down, controlled and precautionary areas will take a polymerase chain reaction (PCR) test tomorrow despite predicted rainfall, said Zhao Dandan, deputy director of the Shanghai Health Commission.Door-to-door sample collection will be provided for those who have tested positive via antigen self-tests and are awaiting rechecks, as well as people living with them, Zhao said.