What is the principle of dense query?

Judging whether they are in the same place by satellite positioning and whether they are in contact with the positive person.

The principle of secret contact inquiry is to screen people who have appeared in the same place and contacted with infected people through satellite positioning. After screening, the local epidemic prevention and control authorities will send text messages to inform the secret contacts.

After being identified as a close contact, you need to isolate yourself for three days and do nucleic acid testing every day. After all the test reports are negative, there is no need to continue isolation.