The first category is people who have been exposed to newly diagnosed cases or asymptomatic infections, including close contacts, secondary close contacts and close contacts with time and space. The so-called close contact in time and space means that in the same period (including after 1 hour), key people who may be exposed to more than 1 hour are in the same place (key parts of multiple cases or high-risk parts of a single case closed space) and within 250 meters around them, from confirmed cases or asymptomatic infections to isolation control.
The second reason for changing the color is that they visited high-risk areas in COVID-19 (including the cell phone signal under my name).
The third category is inaccurate information when reporting health codes.
The fourth category is the investigation and verification of COVID-19 disease prevention and control platform.