BEIJING - To take a bus in Wuhan, administrator Jocelyn Zhang has to scan a QR code next to the door, which reflects a green code on her phone, to show she is healthy. A man alights from the bus to take her temperature before she is allowed to board.
An orange code would have meant she has to be under quarantine, while a red means she is either a confirmed case, or a close contact, and would be put in isolation.
As Chinese cities lifted strict lockdowns, similar scenes have repeated across public transport and shops in the country as it attempts to shape a post-virus future.
The QR codes serve a dual purpose: to ensure anyone entering is healthy, and also for contact tracing purposes should the need arise.
Chinese health authorities on Friday (April 24) reported six new coronavirus infections, down from 10 a day earlier, bringing the total number of cases in the country to 82,804.
The country has played up its use of big data in its attempt to manage the outbreak, touting it as one of the reasons it has successfully contained the virus' spread.
Citizens are required to register for a health code, applets developed by the government to track whether one has been in close contact with a confirmed case, or is at risk.
They are issued through messaging app WeChat and e-payment platform Alipay, ubiquitous in China.
According to Beijing Youth Daily, some 900 million people use the applet on WeChat. No numbers have been reported for Alipay.
Late last month, scientists from Oxford University recommended other governments consider adopting such "digital contact tracing" in a report published in Science journal. They said the virus is spreading far too quickly for traditional contact tracing methods to work but could be controlled if the process was "faster, more efficient and happened at scale".
But in China, there are concerns that the information collected - from travel data to places where one frequents - could be used for other means, said Associate Professor Alan Chong of the S. Rajaratnam School of International Studies.
"Once the genie is out of the bottle, can you really put it back in?" he said, referring to when data has been collected.
Tencent and Alibaba have firmly denied sharing any user data.
But ultimately, there are more practical concerns that pose a barrier to such apps' long-term use.
"There are times the mobile connection is slow and it takes a long time to load," Ms Zhang said.
"I felt very anxious because everyone on the bus was waiting for my phone, which was stuck, so I just told the driver to go."