Over the past week, their Lunar New Year absence prolonged by the coronavirus outbreak, Chinese people have been gradually returning to work. As they prepare to leave their hometowns, they can, or are sometimes obliged to, provide personal data such as recent travel and health conditions on their smartphones, usually through Alibaba and Tencent's apps.
Based on their responses, algorithms will show a health code colored green, yellow or red, signifying the likelihood that they have coronavirus and thus their fitness to join millions of others on the road in China. Those who get a red code must either self-quarantine or be quarantined in a facility for 14 days.
