Compared with before, COVID-19 is more special and more difficult to prevent and control. The key lies in the close cooperation between the input and output places of migrant workers, so that the routine epidemic prevention work is firmly in place. On the one hand, "code plus code" is definitely wrong, on the other hand, the environment and conditions of "one line and one code" are not mature.
At the national level, the risk data service of epidemic prevention and control in COVID-19 is carried out nationwide, and all provinces and departments can call and query the unified database of confirmed and suspected cases, close contacts database and county-level risk grade database, basically realizing mutual recognition of basic data.