Walking, knocking – and more knocking. Community worker Li Feng and her colleague's knuckles are red and swollen, having knocked on each door in two 27-story residential buildings since Monday. Checking and recording 1,000 residents' health status within her jurisdiction – or what she calls – the grid, has become Li's duty in the latest round of citywide screening to uncover the novel coronavirus cases. Taining community in old district of Wuhan's Jiang'an is divided into six grids, each with a designated worker like Li.