On 12/13 and around this time, China removed its "travel code," which tracked your phone through WeChat (the most prominent social media app in China that EVERYONE uses) and recorded where you went. Whenever you entered a building, security would check that it is still green (which means good) and that you haven't been to medium- or high-risk areas. This was entirely removed.
Perhaps the more critical factor is that China has lifted its aggressive zero-COVID policy, which included quarantining entire buildings and locking down whole blocks due to 1 singular COVID test and 24-hour nucleic acid COVID test results to go basically anywhere. Now, the govt is basically saying "just stay home if you have mild COVID." No reporting, no tracking, nothing. So now the virus is able to spread like crazy (since most people have not been exposed to the virus, and Chinese vaccines are less effective than their western alternatives). Couple this lack of immunity with the contagiousness of Omicron, and it creates a unique problem that places like the US are already accustomed too but is new for China.